If you check the scabbard mouth, you may find one marked M8 and the other M8A1. The M8 was shorter and just fit on a belt. The M8A1 was the change of adding the M1910 belt hook and initially they just sewed it in the loop. The complaint was that it would no longer slip over the pistol belt so the longer belt loop was added. Many times you find an M8 that had the loop changed for the long one, and someone will cut the threads and remove the M1910 hooks. You can tell the difference because the loop is so long. The M8 is noticeably shorter.