It's a native copy of a Browning Model 1900, originally made by Fabrique National of Belgium between 1900 and 1914, but sold widely around the world. This particular one would have been copied by one of several different groups in SE Asia (like the Cao Dai, who did the same thing in Vietnam) that are known for taking a genuine original and then reproducing it out of whatever hunks of steel they can get their hands on. It's a fascinating piece of history, but you shouldn't fire it because factory parts likely wouldn't fit as replacements, and the people that made these had no real way of heat-treating the steel they used. If you post some close-ups of the markings on the left side of the pistol, there may be more info, but many of the people that did these simply stamped markings that looked like the originals on their copies.
