Yet another Topps test issue the 1973 Topps Pin-Ups were a 24 "card" set that similar to the unissued Topps Comics of the same year served as the wrapper for a piece of bubblegum. Indeed the Pin-Ups and comics were the same size perhaps two different methods of packaging the same gum. In fact when looking at the reverse of the Comic and Pin-Up designs (the outside portions of the wrappers) it is easy to note that the layouts are virtually identical with coloration and the name of the product being the primary differences. Even the checklists are identical.This example of Dodgers reliever Mike Marshall is an unissued "proof" - an even more scarce version of a very scarce issue. Graded Authentic by SGC the "card" is produced to the same dimensions as the commercially-released Pin-Ups but does not contain the printed reverse with the gum packaging that is featured on the actual Pin-Ups. In this case the reverse is simply a white unprinted background.It is difficult to put a finger on precisely how scarce these proofs might be. SGC"s population reports do not differentiate between the proofs and the actual Pin-Ups. However of the mere 15 Pin-Ups they have graded just four - this Marshall Bobby Murcer Willie Davis and Lou Piniella - have been graded Authentic. It could be that the other three are also proofs.In the case of PSA they also do not differentiate between proofs and actual Pin-Ups however none have been graded authentic. This leads us to believe that each of the 198 1973 Topps Pin-Ups that have been graded by PSA have full printed backs and thus were all legitimately issued.In either case publishing population data on the proofs is moot. This is a scarce and quite possibly unique item from a highly desirable issue certainly one of the most scarce items in this auction.