I totally disagree with what Dean said. The
Kf was the barrel steel mark. On the early steel barrel hammerless guns those with rib markings of Vulcan Steel have the
Kf on the barrel flat --
111056 01 16-gauge, 28-inch, Kf barrel steel.jpg
and those with Titanic Steel and a few Acme Steel barrels have a
K.
105974 02 K in barrel steel location.jpg
In the 130xxx range we begin seeing the V, T or A in a circle barrel steel marking.