Scarce SMLE aim corrector device used to train troops on proper sighting. Nice condition but unfortunately missing the smoked glass that fits scant wise in the holder. Could be replaced with a similar thickness of glass with a gray or dark smoked tint. Last picture shows a complete one with the type of glass needed.
Nice piece of auxiliary equipment to add to your collection of Enfield accessories.
Please check out my other listings for more unique items as well as more like this. I offer combined shipping for items purchased in the same week. That will save you money.