ummm....Wot Glass????
I think most CMP's just had a roll up canvas cover for the rear cab window and this may be why you have no frame or glass for it.
Although I found this photo of an F8a and it shows what looks like a frame and glass.
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Cheers
Cliff Hutchings
aka MrRoo S.I.R.
"and on the 8th day he made trucks so that man, made on the 7th day, had shelter when woman threw him out for the night"
MrRoo says "TRUCKS ROOLE"