The 1S in .338 WM is probably the most desirable of the cataloged 1S calibers, the others being the 7mm RM and the .300 WM. No one knows how many were made, but the .338 was in the catalog for a shorter period of time, as compared to the other two, which were first cataloged in 1970. All 3 of these calibers are now discontinued; I believe the newly cataloged .300 H&H is now the only 26" barrel 1S now available. Several 22" barreled calibers are now in the lineup, including the .338 RCM.
Great elk rifle!
El Numero Uno
a Serious Collector of the Ruger No.1 rifle;
a Modern Classic Sporting Arm