packing unit seal through which a shaft passes, whether rotating (as with most safety pens), or reciprocating (as with plunger-fillers and Moore safeties)
  palladium silver white metal alloy (Pd-Ag) used for some Sheaffer nibs from the '50s on; these were originally cheaper than gold nibs, but this has changed as palladium prices have risen
  PCA Pen Collectors of America: nationwide collector-run nonprofit organization
  pearl short for "pearlescent", referring to celluloid displaying this property; generally off-white or yellowish if color not further specified
  pen we now call the entire writing instrument a pen, but up until at least the 1920s, "pen" was often used to denote the nib alone
  Permanite a trade name for celluloid
  Personal Point Wahl's system of user-interchangeable screw-in nib assemblies; late '20s-'30s (click for illustration)
  PF plunger-filler (see definition below)
  PFM "Pen For Men": short-lived oversized Snorkel introduced 1959
  piston-filler a piston moves up and down the barrel when a knob is turned; the standard for European pens, but in America only used in the Conklin Nozac
  plastic to pen collectors, celluloid, cellulosics, and acrylic (as opposed to hard rubber, even though hard rubber is technically a plastic as well)
  platinum black striated silver-grey celluloid of luminous pearlescence; used in the 1930s by Montblanc and OMAS, a highly prized material.
  Pli-glass Parker's term for its transparent vinyl ink sacs used on Aerometric-filling pens.
  plunger-filler fills on the downstroke by creating a vacuum behind the piston (see Onoto illustration); sometimes called "vacuum-filler"; somewhat tricky to repair
  pneumatic filler the sac is flattened by air pressure, usually generated by a plunger
  POC In Waterman's numbering system, a suffix denoting a screw-cap eyedropper
  porte-crayon metal holder for a short wooden pencil or rod of graphite, which can be extended or retracted
  post to place the cap on the end of the barrel opposite the nib (gently, please!)
  posting fine firm nib designed for bookkeepers posting entries into account books
  Presidential Parker's term for models with caps and barrels of solid gold, from the 51 on
  propelling pencil mechanical pencil; an older term, and preferred in British usage
  propel-repel pencil mechanism that both advances and retracts the lead.
  pump-filler a general term for multistroke filling mechanisms
  push-knob-filler a button-filler with a non-detachable blind cap; the blind cap is unscrewed and then pressed to compress the sac
  Pyralin trade name for celluloid
  RB rollerball (a ballpoint using water-soluble ink)
  repeating pencil the lead is advanced by pushing on the top of the pencil, new leads are automatically fed from a magazine within; same as injector pencil
  resin modern pen marketers' fancy name for plastic
  reverse oblique a chisel-like nib with a tip that angles back at its right, viewed from the top
  RG rolled gold (see definition below)
  RHR red hard rubber; note that the "red" is actually more of an orange
  Ripple Waterman's term for its distinctive ladder-patterned two-color hard rubber pens; most are red and black, other color combinations are much scarcer; not to be confused with woodgrain
  rolled gold same as gold filled; this term is used more frequently in the UK (NB: although there are technical differences drawn between rolled and filled in modern manufactures, this distinction is relatively recent)
  roller clip clip with a rolling ball at its end; chiefly associated with Wahl-Eversharp, though previously licensed to Boston Safety and others
  RR ribbon-ring or ringtop; also known as ladies' pens, though they could be used by men as well, hung on a watch chain
  ruler mark notch-shaped wear on the side of a nib, from bearing against a ruler or straightedge
  sac elastic rubber ink reservoir
  safety fountain pen with a retractable nib; also used prior to c. 1920 to designate a pen with a screw cap and an inner cap, as with the Parker Jack-Knife Safety
  section the tubular piece which holds the nib and feed, usually but not always a separate piece from the barrel; originally "gripping section"
  self-filler/filling eyedropper-era label applied to any pen with an integral filling mechanism, not requiring a separate device (such as an eyedropper) to be filled
  Senior model name for the largest Duofolds; sometimes used by collectors to refer to the oversize versions of other models and brands, often inappropriately, in that most were not so denoted originally
  Signet Parker's term for models with gold filled caps and barrels, from the 51 on
  silicone grease the most useful general-purpose pen sealant and lubricant, and the safest on plastics and rubber; not to be confused with automotive silicone greases with a petroleum base
  sleeve-filler a form of squeeze-filler, with a movable sleeve that covers the pressure bar opening when not in use
  snowflake irreverent collector term for Montblanc's trademark six-lobed star
  Snorkel Sheaffer's pen with a extending tube for clean filling (see Profile)
  spearhead feed original feed for Parker Duofolds, Jack Knife Safeties, and earlier eyedroppers, characterized by coarse sawtooth side cutouts, looking like a barbed spear tip; also called a Christmas tree feed
  Special as used by Parker, either a slender Duofold of Senior length and Junior diameter, or an economy version of the 51 with an Octanium nib
  Speedline Vacumatic filler with aluminum plunger but without the lockdown feature, c. 1937-41
  spoon feed Waterman's second feed design, patented in 1899 (and 1903), incorporating semicircular ink-trapping cutouts alongside the capillary feed channel
  sprung describes a nib or clip that has been bent out of shape by application of excessive pressure or tension
  squeeze-filler fills by manual depression of a pressure bar through a cutout in the barrel or the filler housing
  star clip a clip used on some Vacumatics c. 1939-40, incorporating a five-pointed star, which appears to have been a precursor symbol to the Blue Diamond
  star nib early Waterman nibs with a star imprint; most seem to date to the last years of the 19th century
  Stonite trade name for celluloid
  straight cap small, short slip-fit cap, the same outside diameter as the barrel, which fits on smaller-diameter sections at each end of the barrel
  stub historically, the same as "italic"; now generally used to denote a slightly more rounded chisel-shaped tip
  stud-filler another term for button-filler, most commonly used in the UK
  stylo short for stylographic -- a pen with a fine tube with a wire inside instead of a conventional nib, similar to a modern drafting pen
  syringe-filler fills by pulling on a plunger shaft; a long blind cap is usually necessary
  taper cap a variation of the straight cap, extending in a long taper; not to be confused with the cylindrical cone-cap
  tassie decorative trim ring at the end of the barrel, held in place by a "jewel"
  test mark removal of a small patch of metal with a jeweler's file; crude and usually totally unnecessary method of ascertaining if material is solid gold or gold filled
  thumb-filler another name for a squeeze-filler
  Touchdown Sheaffer's pneumatic filling system, abbreviated "TD" (see Profile)
 tooth friction between nib and paper; preferred (in moderation) by some as more responsive than a frictionless glide; to be distinguished from scratchiness, which is generally used to describe a nib that catches on the paper
  trench pen WW1-era term for an ink-pellet pen, although by all evidence such pens were not actually used in any significant numbers in the trenches
  Triumph nib Sheaffer's conical nib, introduced in 1942
  twist-filler a filling mechanism in which the sac is emptied by twisting it via a knob at the end of the barrel
  two-tone nib gold nib partially plated with a white platinum-group metal -- although occasionally white-metal nibs were given partial gold plating to similar effect
  underfeed the usual type of feed, which lies below the nib
  Vacumatic (Vac) Parker's pump-filling pen, c. 1933-48 (see Profile); or, the filling mechanism used in these pens and in the Parker 51 from 1941-48
  vacuum-filler often used to denote a plunger-filler, but rather confusing since many pens with diverse filling mechanisms bore this monicker or close variants; capitalized, a name used for the Parker Vacumatic while in early release
  vent hole the hole in the nib at the end of the slit, serving both to allow air to return via the feed channels to the ink reservoir, and as a stress relief device to prevent crack propagation from the end of the slit; most dip pen nibs are ventless, while most fountain pen nibs have vent holes; also, small holes drilled in the cap, on slip cap pens, intended to prevent ink from being sucked out when a snugly-fitting cap was removed, and on pens with inner caps, intended to reduce condensation on and adjacent to the section, though usually dispensed with on modern pens; "vent hole" and "breather hole" are often used interchangeably
  vermeil gold over silver
  vest pocket a small, pocketable pen, with or without a clip or ringtop fitting; many ladies' pens could equally accurately be termed vest-pocket pens
  visulated with a transparent area, used in reference to sections; Sheaffer invented the term in the 1930s
  VS Short-lived Parker button-filler, introduced in 1946, resembling a 51, but with a conventional nib; the letters stand for "Vacumatic Successor", though that title more accurately belonged to the 51
  vulcanite another term for hard rubber
  VV clip an early spring-loaded rocker clip, used on Parkers, Conklins, Moores, and others; made by Van Valkenburg, US patent 844061
  warranted nib an unbranded gold nib, typically marked "WARRANTED/14K", "warranted" meaning guaranteed as to gold content; many minor-brand pens originally came with warranted nibs, and such nibs were also widely used by independent repairmen as replacements
  web celluloid pattern with a freeform network of colored lines like a draped net (also called "candy stripe"), or the longitudinal brickwork-like pattern of the c. 1937 "Golden Web" Vacumatic
  washer clip clip with its top end formed as a ring of the same diameter as the cap, and held between the cap body and a screw-in cap top; introduced by Parker in the 'teens on its Jack Knife Safety line
  woodgrain multicolored hard rubber patterned with longitudinal striations, almost always red (orange) and black; not to be confused with Ripple or mottled hard rubber (although, confusingly, Waterman catalogs used "mottled" to denote both true mottled and woodgrain, without differentiation)
  1/8 14K imprint on gold filled components, indicating a gold layer of 14K purity and constituting 1/8 the total weight of the laminate
  18KR not solid 18 karat, but rather a common Italian abbreviation for 18K rolled gold, the "R" standing for "rinforzato"
  375 375 fine, or 375/1000; decimal equivalent of 9K (usually only used in the UK)
  585 585 fine, or 585/1000; decimal equivalent of 14K (though 14/24 = .583)
  750 750 fine, or 750/1000; decimal equivalent of 18K (the legal standard for gold in certain countries such as France and Italy)