Here is a pair of large old polished chrome on steel backplates from the 1950's to 60's for use with round chrome cabinet 

door/drawer pulls.  This is for one pair but there are additional pairs available with discounts on both price and shipping.  

Recently out of a small town Nebraska estate, they are old hardware store stock.   Some of the backplates are in a different

style of packaging, but all are Amerock.