My view FWIW, is that the finned bowl you have is likely its original one.
There is evidence which SUGGESTS that the finned bowls were fitted from VIN 1783 onwards. Service bulletin #13 of 26th Jan 1970 covers the fitting of a modified oil filter bowl (with fins, and a number 2 embossed between two of the fins) to CB750's in the range of VIN 1783 to VIN 9554, due to problems of cracking around the inner boss of the first version finned bowl. Presumably the quoted VIN range covers the range of VINS factory fitted with the first type crack probe finned bowl. I am simply surmising that the replacement was not applied to VINS prior to 1783 because those were factory fitted with unfinned bowls which were not crack prone.
That is only my take on this subject as there are also those whose recollections are that later VIN's than 1783 came from the factory with round bowls. Given I was not fortunate to have had one of these back in the day, I am not going to suggests such observations / recollections to be incorrect. This is just another of those areas of uncertainty.
Chris R.