Great little gun and caliber. It was 7/8's th size of a 1911 and a lot thinner. It used a single stack magazine. Similar to a 1903 Colt Pocket Hammer .38 acp. I've owned two of them. One....was serial number 6.....a nic original Colt, and the other an un-numbered shop 1910 that was stamped .40 Cal. (actually the caliber was 9.8mm). Here are pictures of an empty box with one round of Winchester ammo. Its all I have left.....after selling my collection. I had 3 full boxes of the Winchester ammo....that went with the guns. I'll try to find my pictures of the Colts.