Thanks again for the comments

In the picture below revolver is clearly marked MOD 20 in the crane, its SN#, S155XXX is both on the barrel and the butt frame.

Page 188 of SCOS&W3 shows 1957 as first date of stamped model numbers on the Model 20.
Page 397 of same shows 1956-1957 SN# range as S 150000 to S 175000.

Is it possible to determine the original barrel length of this 38/44 by the placement of the existing barrel stampings?

It looks to be a early one, maybe it is the first model number marked 20? .

THanks again