I cannot remember the name, but there was an outfit years ago that claimed to be able to "re-heat treat" SAA frames so they could accept smokeless powder loads. They may have even believed that themselves, but at the time I talked to some metallurgists and was told rather firmly that doing that was impossible with the old iron frames and that the claim was at best wrong and at worst a deliberate and dangerous fraud. NOTE: I do NOT claim that the company involved was the one mentioned, I simply don't know. But they apparently did not manufacture new frames, only worked over old frames; whether they altered the serial number, again I don't know, but it would seem logical to do so if they really thought they were making the equivalent of a later gun.
Jim
P.S. Iron cannot be hardened or strengthened by any kind of heat treatment. That is why old time gun makers used case hardening to prevent wear on frames and lockplates caused by moving steel parts. Later, after the larger parts were made of steel and could be hardened, case hardening, especially color case hardening, continued to be used by some makers as a decorative feature although no longer necessary.
JK