The Keystone Line of saws was in the Disston catalog for decades and was meant to attract what could be called "low-end" buyers. For a probable explanation of Disston's marketing strategy, read the Keystone 107 article. To read Disston advertising for later Keystone saws, go on to the Keystone 1931 and 1935 articles.

Keystone 107 Handsaw
Keystone line of 1931
Keystone line of 1935