There is no cardboard tube in mine (1952) it is all metal. The metal tube is about 1 inch long and is spot welded to the inside of backing plate. The light socket just snaps into the back. Right near the top of that tube, approx. 1/8 " down from the inside edge, there is a ridge that the lens sits on. Between that ridge and the inside edge there are 4 little "tits". The lens originally fit in between the ridge and the tabs. Not real great on posting pics- I am still a nonconforming rebel!!! Mostly cuzz I just don't do it enough to remember How!!!!! hope u get the idea.
