The unbranded .38 caliber revolver is Thad‘s weapon of choice. The weapon is vastly more accurate than depicted – Thad’s about as handy with a gun as he is with his stick.
Thad’s .38 has a five-round cylinder, is shown to be fully loaded, and is discharged four times over the course of The Dualist. The weapon may or may not have been brought aboard the Sabrosa.