Priming cap : attachment : press fit.
Case : the neck has split..
The .303 cartridge was well suited to soft skinned medium game, and .303 rifles based on Martini or Lee Speed actions and designed for officers to use either for hunting or as a personal weapon were supplied by BSA and others. As ex-military .303 rifles appeared on the surplus market, many were used, converted or unconverted, for hunting and species management. This cartridge is almost certainly pre-First World War, as Eley Bros. ceased making rifle ammunition in 1920.
(Reference: : 1934 : Catalogue of Sporting Ammunition)
Headstamp (stamped, case base, large letter style)