Artists and Copyrights

New York Memories

So- I have a question about artists and how copyrights affect our art.  I am VERY careful about not copying art of other artists, and paint my paintings from photos I take myself.  I would hate it if anyone copied my work, and would not do that to another artist EVER.  Well- I have some NYC subway tokens and thought they would make fun charms for my jewelry in my Etsy shop.  I looked around the internet - I saw many jewelry items using subway tokens, so I thought it was okay to use them.  After all, I am not trying to sell them to use on my subway- or saying that I designed them myself.  I am in no way claiming that I am affiliated with the MTA- or selling them as a token, simply as a piece of art.  My question is- how can recycling  a subway token hurt the MTA in any way?  I think I am free to sell these out-of-use tokens on ebay or at an antique store, so why not as a charm?

This necklace has been listed on Etsy for some time and out of the blue, I find out that it infringes on a trademark and I cannot sell it.  My main problem isn't that I cannot sell the necklace, but that MANY items like mine are available with a simple Google search.  Maybe I should have one of these other artists sell my item for me since they are free to sell them.