I believe you are correct. I think I read that the 61 GM dog dish hubcaps are chrome plated copper. The 61 full hubcaps were stainless steel. The repo dog dish are stainless steel.If I were a betting man i'd say the originals will be all metal, and i'd guess that the repo's will either be a combination of metal/plastic or if all metal will be more cheaply made & weigh less. So, if the repo's are good quality & metal then a set of scales may well be your friend.