This weekends find, 1915 Westinghouse M91. Has Accuracy Stamp & Proof of Aim, scrubbed imperial eagle. No [SA] stamp. No import marks. Russian stock with pressed sling escutcheons. No refurb stamps. Blued Bolt. 94x,xxx serial range.
What is this mark on the barrel shank? Kind of like a grenade.
Thanks!
What is this mark on the barrel shank? Kind of like a grenade.

Thanks!