Arthur---for 55 years there were 4 unknown subjects in the baseball subset. This is in my view the hardest actually issued Topps set to put together. Bob Lemke has a piece on his blog about filling in 3 of the 4 on the the checklist with these 3 cards found not long back by a collector.
I was fortunate to get these when the seller let them go
Bob has concluded that the 4th missing player is Hal Smith so the baseball checklist may be complete....maybe