Different 1570 movement, Sports and DJ?

[Fredrik]

Hey,

I was always under the impression that in the old 4-digit Rolex watches, like a 1680 Submariner and say a 1601 DJ, the movements were slightly different.
This is visible in the two shots here, the DJ movement has a bevel on the dial side on the plate.
There is a thread on VRF now were someone is looking for a movement for a 1675 and asking if a DJ movement would do it. Even if fitting the needed parts for the 24 hour hand, it would still be obvious that the movement isn't original, wouldn't it? I assume this is not a part easily obtainable?

[Fredrik]

The part that differs is the calendar wheel retention ring, just learned that.

[Fredrik]

Well, I found some schematics...
It's called a "date indicator seating" I think. There seem to be at least 5 different types, I found:
part no 7956 for 1500-series Date watches
part no 7963 for 1600-series DJs with a diameter of 27.86mm
part no 7964 for the 1625 TOG with a diameter of 27.20mm
part no 7965 for at least the 1675 GMT with a diameter of 27.20mm
part no 8131 for the 1530 and 1630 automatics in oysterquartz case, diameter 29.46mm

Note that the 7963 and 7964 has the bevel for the pie pan dial(I think).