Being as brief as possible but touching on what I believe are pertinent facts:
I have a 1990 740-GLE with the 16 valve engine. I puchased it at around 90,000 miles. It has a "belt change sticker" indicating the timing & balance belts were changed at 89,100 miles and about a year ago. Current miles are 94,000, about 5000 since the sticker says the belts were changed.
I just removed the upper cover from the timing belt because I wanted to know, assuming the belts were changed, did the tension have to be adjusted. Fortunately my 740 has the newer self adjusting tenioner but I've been a little uneasy about trusting the sticker as the change mileage of 89,100 is before the regularly scheduled change-out of 100,000.
A good friend of mine that has much greater Vovlo experience and knowledge than I said that a oil pump change out could have been done and since they were at it they probably replaced the belts at that time or the previous, and now deceased, owner was the cautious type as illustrated by the carefully stamped maintenance book and had it done earlier that scheduled because of the horror stories you hear about engine damage if a belt breaks.
In any case I've said all that to ask this. If the part numbers, timing marks etc. can be clearly seen and read on the timing and balance belts is there a fair chance they were replaced about 5000 miles ago or can these be clearly read at 50,000 miles as well? I just don't have the cash right now to pay for the work and if I can put it off until the next 50,000 miles I will otherwise I gues I'll have to go the route of the dreaded credit card.