This box holds 25 7’63 mm Mauser cartridges from the Sevilla Arsenal in Spain.
The box is made of an unusual light blue cardboard.
The box is peculiar because the norm was to pack these cartridges loaded in 10-round stripper clips for the Mauser or Astra pistols, two clips to the box, hence 20 rounds to the box. Sevilla ammunition packed this way is well known.
Another peculiarity is that the bullets show signs of having been loaded into cartridges more than one time, judging by the dot crimp marks. Some of them show two early sets of crimps, that held the bullet in place in two previous occasions. This would be the third time these bullets were loaded!
Bullets have a lead core and a cupronickel jacket.
The 7’63 Mauser cartridge is known to be very prone to case neck splits; in fact most of the rounds in this box have splitted. So the ammunition would become unusable, but the bullets could be salvaged for further use.
In a visit to an Army arsenal in Madrid, in the mid-80s, I was told that if you took out crates of this caliber ammunition from the stores into the sun, soon you could hear the “clicks” of the case mouths splitting due to the temperature change.