Here are 3 detail pictures. I share so that maybe we can further determine maker and era:
Buttplate is marked Germany and trade available in the early 20th century.
The grip cap also available to the trade in the early 2oth century. Common English scroll engaved
The last is of the cheekpiece and you can see the detail of the cut shadow line. If anything, this may stir some thoughts as to who did this detail: