I wound up with a couple of GRF trade gun locks after switching them out for the Davis replacement locks, for customers.
My old chiefs grade, thirty inch barreled, trade gun, had a Lott lock in it, and shot fine. I gather it was the exception. the rule seemed to be that the frizzens were soft, and needed case hardening, to make them spark. Some of these Lott locks have pretty good geometry, and others don't. Turner Kirkland said, that the companies in Italy that were making replica guns, and parts, traded some of these lock, and parts, molds around, so when molds got worn and needed remaking, they weren't always made the same way.
Of the three Lott locks I own, two have pretty good geometry, and frizzens that take a case pretty good. The other one is marked by GRF and has poor geometry and a frizzen I have no idea how to make work. It is either butter soft, or hard as glass, drawing the temper seems to be all, or nothing, with this piece of steel.
Hungry Horse