of a CG that predates mid 50's.
The 6152-1 serial number (124XXX) puts these watches (according to Rolex Geneva, if asked on an individual watch) in 1954-5.
It may well be that the CG was developed at an earlier stage and that post war financials/priorities/etc. prevented from this invention to realize. But until proven otherwise, I think the CG was used first on 6152-1 in the mid 50's. I also think the 6152 and 6154 predates this.
Ahh, the mysteries of Panerai,,,,gotta love it
Asi