This is an original accessory for the M1917 series Enfield rifles. Since these rifles do not have a magazine cut off it is difficult to teach bolt manipulation without removing the magazine follower and spring. This device was developed to allow the magazine follower to be made to sit lower allowing the bolt to be cycled without catching on the rear hold open edge of follower. It has ben used by some as a "single shot" loading platform for range use. Condition is still in the original grease ready for you to clean yours up. The one in the photo is cleaned to show detail. These are shown in the original manuals and in some collector books on the M1917 Enfield.
