I have a question about dogdish caps

[dk1972]

i just bought 3 dogdish caps from my local junkyard for $30 two have the yellow emblems and the other one has blue emblem. but the yellow ones centers dip in and the blue sticks out. why is this? did they change in the years? here is some pics of them the yellow ones are pretty much perfect besides i need to repaint and the blue one has a few small dings that can be fixed. it sucks because the junkyard only has these 3 i just need one more ha thats life i guess its going to be hard trying to find someone who wants to just get rid of one lol