Even more recently, in Edinburgh in the mid-50s at the beginning of the Skiffle era, there was one music shop - Rosenblooms - with a stock of "Black Diamond" Hawaiian guitar strings from pre-war days. That was our choice then until, I think, "Cathedral" strings began to appear.
Gauges? Huh! We had 1sts, 2nds etc. Strings breaking at the bridge end were often re-fixed to the little bronze ring at the end! Strings that went "dead" were often carefully coiled and boiled then put back on the guitar.
From a bit later I remember strings for electric guitars which were coated in black plastic to avoid squeaks - they were rubbish!

Eddie