Well I can tell you that your helmet is German from WW1. the "lugs" were originally to attach a face shield. No idea on the others, but the helmet is a cool find!
Also I think the chain is from an old chandelier, I know I've seen similar ones here.
Thanks guys now for coin I will be soaking in Olive Oil to see if any more details emerge. It's hard to make out in the pic. but I can make out the word "UNITED" on the circumferance on one side. I can just make out an impression of a woman facing right on the other. Which fits with a large Cent. Measure's 1"1/8