Ok, so i've had this old TLR sitting on my shelf for ages and today i thought i'd see if i could 'fix' it. The focusing knob was stuck and that was my first item on the agenda. After a while i managed to get it open and see what the problem with the focusing was, it was simply completely stuck due to old grease and dust.. "well, problem solved", i think and start cleaning it. After im done with the screw mechanism for the focus i decided to give the mirror a good once over too.. that was a problem. This was no ordinary mirror at all. Its a piece of glass thats coated with some very fragile reflective material on the "business side" (the one that reflects). It promptly got a cyan/magenta coloured haze and i rubbed straight through the coating. I'm thinking i could just have a regular mirror cut to size and that will sort the issue, but there is probably some reason for the mirror to be made this way, no? So would any of you know what kinda purpose this mirror had (if any)?