TD Bank customers in Maine and around the country saw the shiny “Penny Arcade” coin counting machines unplugged, covered up and eventually carried away from the lobbies of their local branches last summer. In recent weeks, they’ve received cards in the mail hinting at why: a notice that they were eligible members of a class action settlement against the bank over the Penny Arcades, which had allegedly been shortchanging customers for years. The problem with the festive machines was first uncovered by NBC television’s “Today” show, which in April 2016 tested machines at five New York City TD Bank branches and found all of them were undercounting, some by a penny or two on the dollar, one by 15 percent.