I show here the box front and top view for this 8x51 Cartridge:
AND THAN THE SIDEVIEW OF THE CARTRIDGE AND THE HS.:
As the stamped 366 on the box shows a Suffix I (which does not exist) it is maybe the correct L (which exist),
but the bullet Nr 117Z does not exist either. The bullet is the 8-21 (= 8mm Caliber and 21mm lenght).
The headstamp is the M88H and not the corresponding number 366 L, and I do not knew, if the 366L exist…in a headstamp