Written on case: “8×74 Keller Magnum (made from .348 case). Exists also with steel base.” This is a 2 piece case.
Bullet Diameter:         8.11mm        Case Length:   73.80mm
Mouth Diameter:        8.78mm       Neck Length:   13.07mm
Neck Diameter:          8.88mm        Shoulder Length:  52.00mm
Shoulder Diameter:  13.42mm
Base Diameter:         13.86mm
Groove Diameter:     11.84mm
Rim Diameter:          13.86mm

This might in all probability be the same as the 8×73 Miller & Greiss