There are at least half a dozen Lincoln Jeffries pistol variants where the cylinder is in the grip, some apparently one-offs, others made sporadically in very small numbers. Yours, as it says on tin, is the Lincoln, the most numerous one, but even so, very rare. A very nice example, but it has been reblued using a method that wasn't around when the pistol was made, as evidenced by the purplish coloration on some of the steel parts, which may be cast rather than forged.