The pictured rifle is a Mannlicher-Schoenauer, and listed as a ".375 Express" it could be either a .375 2-1/4" Rimless Nitro (9,5x57) or a .400/.375 H&H, most likely the former.

I have owned an H&H Mannlicher in the .375 2-1/2" Flanged Nitro, and a beauty it was, but it was built on an 1892 Mannlicher en-bloc clip action, not the later spool magazined Mannlicher-Schoenauer action.