My first impression (never trusting digital images) I thought "Photoshop". In the early days of Digital photographs the Court Systems would not accept them at all. Then, after the technology was undeniably the way of the future, the expert witness submitting the digital images had to sign an affidavit "under the penalty of law" that his digital images had not been altered nor enhanced. Photoshop aside, giving this some serious evaluation on the OP's word of honor that it is NOT a Photoshop-ed image, here goes:
From the placement of the number and spacing it seems there should be 3 numbers prior to the "25", as if it had been numbered xxx25. Compared to other serial number, the justification to the far right doesn't correspond with placement of 4 digit serial numbers but more to a 5 digit serial number.
Model 39s went from 4 digit SN, to 5 digit SNs to a final 6 digit SN up to approximately the 110000 range (Rule of thumb). I will agree the 25 and MODEL 39 look nice but that is a much later frame, very long duck tail. Long extractor, serrations etc.
Whatever this is or is not, it is interesting ... but ... it is NOT the missing link or lore, myth and legend that we've been looking for.
I am also trying to get a perspective of the thickness of the side of the frame to the front of the slide where it drops off. It seems this side of the frame may be "thinner", perhaps milled and re-stamped, or, perhaps it is NOT milled and restamped. Or this could be the product of "the Great Pretender".
The finish of the alloy frame is basically a baked on "paint". There is much that can be hidden underneath that "paint" that you cannot see unless the paint is stripped. When a classic car owner came for a full body restoration I would make a conditional estimate of the refinish, to be reviewed again, AFTER the entire car was stripped when I can see the metal beneath.
If this letters out as a genuine Serial Number 25, I would be shocked. And, if it does letter as Serial Number 25 the ship date has to be mid to late 1960s by the production changes noticed. Even if a special order serial number (if S&W did such) the numbers are entirely misplaced. It would be expected that the 25 would be centered over the MODEL 39 such as is in the 4 and 5 digit serial numbers. Much later into the later 6 digit MODEL 39s when transitioning to the 39-2s, sometimes are justified to the far right last number of the serial number in line with the 9 of the MODEL 39 stamp.
No matter which, at very minimum, it is interesting.
