Okay, well I heard that in 1990 there was around 3,000 proofed pennies made at the san-fransisco mint without the "s" so people thought they were from the Philadelphia mint. However, no pennies were "proof" - minted in Philadelphia that year... So it is an easily distinguishable error. Anyways I was searching through ebay and found an item titled "1990 Lincoln Cent lot of 3 (P & D)" I clicked it and it said they were proof and uncirculated. When I looked at the picture there were 3 proof pennies from 1990 and one of them had no s... I just bought them all Here is the link http://cgi.ebay.com/1990-LINCOLN-CENT-LOT-3-PROOF-UNC-P-D-COLLECTOR-SET-/330447167117 What do you think? good deal? it was $4.95 for the lot.