Beautiful saw likely ca 1900-1920. Great etch. The No 12 London Spring Refined was the top of the line Disston offering. 26" long straight blade with no kinks or bends. Clean smooth saw plate noting some oxidization, light pitting, and oddly two spots of heavier pitting on the backside. This will make a fine working saw. Etch on blade reads:
EXTRA
HENRY DISSTON & SONS KEYSTONE SAW WORKS
PHILADELPHIA, U.S.A.
LONDON 12 SPRING
EXTRA REFINED WARRANTED
PATENT GROUND
**All edge tools may need to be sharpened/honed before use**