I don't know that there was any way to tell the diff between the '55 and '56. (Or was it '56 and '57...) Technically it was a Continental, not a Lincoln; for that brief moment in time Continental was a true separate division, & about all they shared with the Lincoln was the engine. Ford made just one or two proto convertibles; I think at least a couple of other MK II's have been reworked as convertibles since.