Welcome aboard.
It could be that the darn thing is just old, but might also be from something that was used to clean the cluster. Your best bet in finding a replacement is either the salvage yards, or hopefully someone here (or at vannin.com) might have one.
It might help if you could remove the cluster and find the Ford part number on it. Here is a picture of what the 69-74 cluster looks like, and where the numbers are located. If the bezel (part # D1UF-10876 on this one) doesn't unscrew from the cluster on yours, then the part number may just be on the back of the whole unit.

The number on yours will probably start with something like D5UF, D6UF, etc. The part number will probably have the same "108" in it, but the last 2 or 3 numbers may be different.
Good luck.