Look at picture: http://www.collectibleamerica.com/coins/5-decades-of-s-mint-proof-lincoln-cents.html I'm pretty sure those proof coins were struck in Philadelphia lol.
The US Mint didn't fail, Collectible America did by not using S mint marked coin images. It also appears to be a 1968, 1975, 1985, 1995, 2005. Why a 68? That's NOT 5 decades of cents.
65-67 had no proofs, only Special Mint Sets, so they had to go with 1968 for the next proof coin Richard
"You could spend up to $200 to acquire the five US Proof Sets needed to acquire these five Proof Lincolns, but we’ve made it easy and extremely affordable with this exciting new collection!" You could also spend just a few dollars to get these 5 coins as well. TC