In the 1970's and 1980's, the Lott locks were the only trade gun sized locks available to builders. Pedersoli still sells a trade gun with a Lott lock. Back then the Lott locks were not highly regarded for performance. Curley Gostomsky could tune them up for his Northwest Trade Guns, but he tired of getting the Lott locks back for further tune ups and he developed his own lock. That said, Lott locks can be tuned to be good performing locks.
@Mertoi has a good-looking Northwest gun shortened in the barrel and has a rear sight added. Not an uncommon period modification. Knap the flint to restore a good sharp edge and let us know how it shoots.