Ed,
Those are very sweet little pistols. And you got a bargain (we won't use the word "steal"...), about 1/4 of its value. They came in .38 and .380, the .380 are supposedly worth a bit more. 65,000 units between 1918-1926.
Iirc the action is kind of a delayed blowback with a separate, tipping breechblock--an unnecessarily complicated design by John Pederson, of 1903 Springfield Pederson Device fame.
They are extremely well made, very elegant, the fire bluing is truly exquisite. Looks like yours has never been fired.
Here's the one I owned briefly before I traded it for a Luger...
--Dwight