Nope, not rare.
There were 3 variants that I know of:
Rev A
Rev 0
Rev 1
No idea what the differences between them are.
Here are some examples of date codes taken from the photo's I could find on the net.
Rev A - Week 48 1993
Rev A - Week 05 1994
Rev 0 - Week 52 1992
Rev 0 - Week 06 1993
Rev 0 - Week 10 1993
Rev 0 - Week 11 1994
Rev 1 - Week 50 1995
As well as being 3 revisions, there were at least two variants (-01 and -02) again I have no idea what the difference between the two are.