[Tijeras_Slim]

Not only that, but Smith did everything they could to make .44 Mags. I’ve seen a Smith .44 Mag from that year marked Mod. 57 in the frame (.41 Mag). They grabbed every N Frame part they had.

[LouAvul]

I don't think they stamped the model number till the gun was finished. What you saw must have been a conversion to 44 mag from the 57. All they'd need would be the barrel and cylinder.

They used the 'N' frame for the 27, 28, 29, 52, 57 and 58. The frames already had the serial numbers stamped and when they assembled the gun, would stamp the model number.

But innovative fellows could come up with all types of conversions. I've even seen the 28 converted to 44 mag.