Battlefield experience in World War I led to some more small external changes, completed in 1924. The new version received a modified type classification, M1911A1, in 1926 with a stipulation that M1911A1s should have serial numbers higher than 700,000 with lower serial numbers designated M1911. The M1911A1 changes to the original design consisted of a shorter trigger, cutouts in the frame behind the trigger, an arched mainspring housing, a longer grip safety spur (to prevent hammer bite), a wider front sight, a shortened hammer spur, and simplified grip checkering (eliminating the "Double Diamond" reliefs). These changes were subtle and largely intended to make the pistol easier to shoot for those with smaller hands. No significant internal changes were made, and parts remained interchangeable between the M1911 and the M1911A1.