I go with antiques being 100 years old or more, and with vintage, I am pretty flexible as to the age, and sometimes just use 19XX's Vintage in the title or description.
I wouldn't use retro, as that usually means something newly created that tries to look like something from the past.
Of course, most people these days follow no such conventions, and freely misuse such descriptors, in the same way they misuse industrial and heavy duty.