Hi
Yes you are correct there is a metal plate/frame fastened with 10 screws that looks to hold the glass in. I just assumed, obviously incorrectly, that sometime in the past the glass had been removed and with no seal available silicone mastic was used. Now this gives me two other questions what was used on the cars originally as I think silicon mastic as we know it was not around in the 1940/50s? And I wonder what the rubber seal I received is actually for? I received the order last August and was just about to try to do the rear screen. I will now not bother, at least for the time being.
Thanks for the info.