I picked up this gapper tool (See Pic 1) at the flea this morning. I'm told they were all the craze in the 70's, but I suspect this one could be a much earlier example. The patent ("2,645,142") marked on it (see Pic 2) was granted in 1953 and first shows up in Herbrand's 1954 catalog, No. 55M, in Section 11, Page 3 (see Pic 3 for a better image from a later catalog), which is page 54 overall in the pdf hosted generously on Mark Stansbury's IA/ITCL, and the script branding looks earlier to me. On top of all that, entries in the later catalogs talk about improved versions that don't match these features.
Either way, I am 99.9% sure these were made by a third party. If you look at the bottom of the excerpt I made from the USPTO site (see Pic 4), there is a huge clue. Give up? Note that while the patent was granted to Otto Schwenzfeier, he assigned it to James T. Clark. Look where Mr. Clark is from. Fort Morgan, Colorado, the home of Clark-Feather, just the kind of outfit who would make these. Heck, they made valve lifters for everyone else, too. I could be wrong, but if I am, it would be a very weird coincidence.
Some close-ups in Pics 5 & 6.