What's the date on the receiver?
You have an 1889/96 bolt, so it could be chambered for the GP90 round instead of the newer GP11 round?
I have a sporterized 1889 at home with no magazine chambered in 7.5x53.5mm.... It's a wall hanger for now.
Cheapest mag I found for the 1889 at a gunshow was $90... (the 1889 ten round mag)
Better off buying a new K31 for that price!
*EDIT* Also, yours appears to have the newer tangent leaf sight instead of the older quadrant leaf sight... looks to have been chambered for the GP90 round.... Hmmm...
Paging Diopter!