Thank you, gentlemen!
I recall that my father's 1906 Winchester pump .22 would accept shorts, longs and long-rifle cartridges, so I've ordered six rounds of the Longs as a precaution. (Thank you, KJ, for the link, since I would be giving my friend a Christmas gift anyway.) However, here is the archived advertisement for the long-rifle cartridge which apparently was promoted for the piece:
(http://i2.photobucket.com/albums/y30/RichardS/Marlin1892Ammunition.jpg)