The Shawk & McLanahan revolvers are a lesser-known example of a very low production Civil War era revolver not made in the Confederacy. Abel Shawk was manufacturing entrepreneur in St Louis making fire engines when he decided to take up arms manufacturing instead. He partnered with J.K. McLanahan who acted as a financier for the project, and with a young German immigrant gunsmith named William (Anglicized from Wilhelm) Tegethoff.
Shawk apparently built his own rifling machine, and sourced many of his other tools form an acquaintance named Charles Rigdon. Ridgon would go on to move to the South and work on several revolver making enterprises for the Confederacy during the Civil War. This led to an assumption that the Shawk & McLanahan guns were also affiliated with the CSA, although they were actually not.
Only about 45 or 50 guns were made before the business venture fell apart, and the surviving examples are all slightly different, suggesting that a final production model was never perfected. The workmanship is quite good, though. The example we have today was actually plated and presented to a Confederate officer by his men, along with a very fancy metal holster.