Yep, 57 Buick , the plastic centers are available through the aftermarket. As a side note the caps to the right of them in the picture are 63& 64 big Fords that came with 15 inch wheels on the 427 cars (hard to find wheel cover if it is an original and not faked one with a 63 Galaxie spinner added to a 56 Mercury wheel cover), below that is a 61 Dodge and last is a 55 Merc.
Chrysler's to the left.....jokers to the right....here I'm stuck in the middle with youse Buick's........