Not sure you'd see any difference externally - both 7730 and 7733 would have to be modified to step down to 15 minute registers. It would be a case of open up and see.

The 7730 is a practically untouched Venus 188 whereas the 7733 has more Valjoux modifications. I believe the 7733 was intended to replace the 7730 but they seem to have carried on alongside each other for a while before the 7730 was phased out.

I was quite surprised when the Belgian Congo Carreras were found to have the Vj.7733 inside, having automatically assumed it was the readily commercially available 7730. Heuer must have adopted the 7733 for production not long after Valjoux launched it.