York does sell replacement parts. I got a few parts for a York leg press I used to have. Also checked on some parts for a machine I was going to buy but decided not to. Usually got a reply back in a...
First one looks like a 3rd gen from the 60's. Is it cast on both sides? 50lb plate with the "B" is 2nd gen, 50's. Third one with nothing on the back is 1st gen, 40's.
One on the left is a 40's wide letter. From what I have seen the 50's style had the 2 1/2 all in a straight line going down the plate. Like atty said the other one is newer 70/80's or maybe even 60's
The backs blank on the 35's like the smaller plates you have? I missed a pair of 35's local last year and saw a pair while out of town but couldn't get them back and didn't want to pay shipping...
The SS would be the Sinking Spring's foundry. I have a bunch of billard plates but never did much research on them. The billard plates with the B on the back could be from the 50's like the weider...