This is not an answer to your question, but here are some notes re alloy car
XK120 - PB60/79A - This was different for the alloy and steel cars. The
alloy cars had BD 1369 backlight with glass only listed. There was no
listing for rubber buffers.
All the steel cars used the same BD 4405 (assembly) and glass BD 8070, with
4 rubber buffers on the frame (no. 2179). The assembly was the same as for
the XK140 RS (see PB152).
Bruce Carnachan’s notes: early cars had glass rear window, later cars had
670178 - Jag World Jul Aug 94, page 44 photo: caption states that domed
nuts on rear window frame are chromed, and “shape of frame is slightly
squarer than later cars”. Looking at the photo, it is not 100% clear
whether the frame is slightly squarer, but it might be.
Material: glass or perspex? Jim Canedy says re Mk V DHC that his rear
window was actually glass.
I will send some pics off list and copy Jim K.
Again, they are of course not a direct answer to your question and indeed
with one car you will have to form a view as to whether these alloy cars are
The best tip was the Mk IV DHC rear window. I don’t have a Mk IV spare parts
book but the MK V book I have shows the “Backlight Complete” at page 114 as
part no. BD4094 which is of course different from either XK120 “assembly”
A pic of the MK IV rear window at page 100 of the Service Manual I have is
not all that helpful but does seem to show the rather squared off corners
Jaguar XK Motoring Historian