That echoes something I brought up in the forum several months ago, "Best Selling Glove of All Time?", in the General Glove Discussion forum. In that forum, it was generally speculated that the RBG36 was probably the best selling glove of the "modern" era, with the Ken Griffey, Jr. endorsement being the most prevalent, so that discussion would support your supposition, BretMan, that his would "pop up the most." Someone in the forum wrote that, at one time, the Dale Murphy endorsement was the most prevalent. I would guess that Cal Ripken, Jr. gloves would be plentiful, too.
I asked a related question in a different forum thread. (My mind moves in circles, but it still gets off-track!

) What endorsements will be valuable to collectors 10, 20, 30 years down the road? The consensus was that fewer endorsements are going ON gloves these days, and the endorsements seem to be going on the department store quality gloves, which are going to be much less desirable to collectors: ex, the RBG36, which is no longer of high quality. Few HOH, Pro, A2000, WorldWin, higher quality gloves are being endorsed by today's players. I may be wrong about this, but at least, that's the way things seem to me!
Players still "endorse" gloves on the Rawlings, Mizuno and the Wilson web sites ... any ideas why their facsimile signatures don't appear on the higher-end gloves that are similar to their gamers?
Yes, I still have my first glove.