Otherwise known as a broken shell or ruptured case extractor for .303 Brit.
Early Machined Handle Type
Marked "VSM" (Vickers, Sons & Maxim)
All have visible manufacturer and proof markings. Commonly used for Vickers and BREN machineguns.
This is a great tool for extraction broken shells from many types of gun. We've even seen it used on M249 5.56 machine guns.