as far as I know, the rear parcel shelf and door cards were always vinyl
the number of hides greatly depends on the size of the hides. typical full size hides are 50 sf +/-. some hides come in 25 to 30 sf size ... which would obviously take more. remember hides are very irregularly shaped as they come off the cow - there are narrow pieces from the legs.
now for the longer discussion and perhaps more than you want to know - buy leather that is made for the automotive / aviation industry that is more stable for u/v light. you should also understand that there are 2 basic types of dye process used on premium hides. one is a surface dye, the other is an aniline dye which completely penetrates the hide. if you deeply scratch the surface dye it will be a more natural color inside ... this means both front / back surfaces are the finish color ... it just doesn't greatly penetrate like an aniline dye does. please also know there are different types of tanning / finishing processes for different types of leather. some will patina others will remain consistent with U/V light. there are vegetable tanning and chromium tanning processes. vegetable tanning is an older process used today more by bootmakers and saddlemakers. chromium salt tanning allows for a softer hand and a broader range of color
there are also 2 different versions of the top grain leather - full grain and corrected grain. full grain has not been sanded or buffed ... it retains the grain layer of the hide - original texture remains. corrected grain has been sanded or buffed to allow the dye to be better absorbed and minimize the appearance of blemishes ... which allows a more uniform color. i greatly prefer the full grain leather over the corrected grain.
as far as I know, the rear parcel shelf and door cards were always vinyl
Michael, all really good questions ... i honestly do not know for sure. i would assume that it was a surface dye and probably vegetable tanning - (aniline dyes and chromium salt tanning is newer).Very interesting. Baring your points in mind, what did BMW use originally for their leather interiors? Surface/aniline dyed, what tanning process?, corrected/full grain?