Trench Firing Device?

[Promo]

This rifle originates from the Bob Faris collection. It has tag no. 150. Skennerton describes it as "Gun Training Aid", and in detail "S.M.L.E. Mk III converted for practice on larger guns. Locating point & spring-loaded plunger on right side, brackets are fitted onto left of action body", as well as "Downgraded rifle for use as small calibre in training with larger guns" and "Cocking piece modified for use with a gun lanyard, an interesting item".

If I was to make a guess, this thing was used as cheap training with large artillery. At least I know similar usage of other guns in this fashion.

Edit: re date, barrel has date of 1914 on it. Skennerton lists maker as RSAF Enfield 1915.