Let me clarify. They fit perfectly on the watch, and may indeed be NOS Heuer. I just don't like the cut of the crystal, its not exactly the same as what I believe is the original.
The original seems to have a more rounded top, this one has a slightly different top cut which IMO detracts from the beauty of the dial by slightly blocking the view of the very outer edge. Hard to describe the difference in words or even photos (I've tried)...but this is mostly visible on the 2447NST where the outer track is not as visible compared to the original crystal. Honestly the difference is negligible, and only those with OCD like me may even notice.

: So when they advertise them as "NOS Heuer" are they
: actually not? I assumed that all 2447s and 3647s would use the
: same crystal size, so there shouldn't be any variance on their
: end.