Mabie Todd Swallow, c. 1935
The idea of a single writing instrument incorporating both pen and pencil goes back a long, long way. Combination dip pens and pencils were already being made in the 18th century, and in the second half of the 19th century numerous ingenious patented designs offered a variety of novel means to retract and extend nibs and nozzles, by virtually every possible combination of pulling, pushing, sliding, and twisting.
Mabie Todd retracting dip pen & pencil, c. 1880
Schnell Penselpen, c. 1929
Not surprisingly, there were early fountain pen combinations as well, but their popularity was decidedly limited. One of the first to be made in significant numbers was offered by Eagle in the 'teens: a screw-cap hard rubber eyedropper, with a pencil end carrying 2mm lead. A bit later, a number of German makers offered metal-overlaid combinations with extending pencil ends, using the same sort of mechanism used for magic pencils. None of these designs gained widespread acceptance, but things changed suddenly in the later 1920s and 1930s, at least in the United States: there, combos became all the rage, produced in huge numbers. What touched off the fad is not entirely clear, and it may have been nothing more than an expression of the love of gadgetry so typical of the America of that era. What is clear, however, is that the vogue for combos predated the introduction of pen industry veteran Julius Schnell's Penselpen -- a combo highly prized today, but a venture that eventually bankrupted Schnell. Schnell claimed credit for the pen-pencil concept at the time, a claim which has too often been repeated uncritically since.
Waterman Ripple combo, c. 1930
The majority of combos from this era were from second and third-tier makers, and ranged in quality from quite good to quite bad. For the most part, top-line makers did not embrace the combo. Parker, Waterman, and Wahl-Eversharp combos are particularly scarce, and do not appear to have been advertised or catalogued (Waterman's desk set combo excepted, along with some of Wahl-Eversharp's lower-end combos). Sheaffer and Mabie Todd combos are more common, while the scarcity of Conklin's "Ensembles" lies somewhere in between.
Keystone & Beaumel Durabilt combos, early 1930s
All-metal combos were also popular during this era. Most of these were produced in the New York City area by firms such as Edward Todd, Hicks, and L.T. & Sons, and were often sold by (and bear the retailer marks of) prominent jewelers such as Tiffany, Cartier, et al.
The vogue for combos did not spread much beyond the United States, so European combinations are not at all common. There is one sort of Japanese combo that is frequently seen, however, which is a variant of the low-quality novelty jumbo, made chiefly for export.