http://www.rockislandauction.com/viewitem/aid/64/lid/1508

The Radium was the predecessor to the much more well-known (and more successful) Ruby pistol made by Gabilonda y Urresti, which was sold to the French Army by the hundreds of thousands during World War One. The Radium was very unusual in its magazine design, which featured a spring loaded sliding grip panel instead of a detachable magazine. To reload, one would push the locking catch and pull the left grip panel down, drop loose cartridges into the magazine area, and then latch the grip panel back up into place.