Impossible to determine without photos.
A crown over U, E, G, N, R, B, S, V, or W are German proof-marks [for different types], a Crown over R or PV denotes Belgian proof, while, as jethunter pointed out, a Crown over BP [or BNP or BV or BP] denotes Birmingham proof, a Crown over V or intertwined CP denotes London proof. Because all Rigbys were actually completely made by Mauser, they carry both German & British proof marks. A Crown over EL, F, S, PJ, P, R, P, PM, PS denote French proof, a Crown over FE denotes Spanish proof.
I could go on & on & on.
Plus, do not forget that early M98 Mauser actions were small ring actions like the pre-98 M95 / M96 versions.