Howdy
Real nice. I particularly like the Gold box and all the goodies.
The K-38 first appeared in 1946. The 38 M&P Target Model, with adjustable sights, had been around for a long time, but the K-38 featured the new Micro Click rear sight with the large, easy to use, adjustment screw. Yours has the 'speed hammer' that was common at the time, It appears your K-38 has the heavy barrel. It also appears the front sight is pinned in place.
Early K-38s had a slightly tapered barrel with a narrow rib. Later S&W went to a heavy barrel with a wide barrel rib.
The K-38 at top in this photo with the funky fake stag grips left the factory in 1957. It has the heavy barrel and rib. The one below has the slightly tapered barrel with narrow rib and pinned front sight. It left the factory in 1950.
This photo shows the two different barrel styles. I should also mention that the Patridge front sight on the newer gun was modified after it left the factory to its present shape.
I'm curious about that serial number. 901xx.
Is there a K prefix to that SN? I'm pretty sure all the K-38s had a K prefix.