This box must date from before 1917 because that year a decree was passed ordering that all the ammunition boxes had to bear a tax stamp, which is lacking here.
The top cover says Taller de carga: Madrid, which means Loading shop: Madrid.
I believe that these cartridges were loaded in Madrid from SFM primed cases. I am not so sure about the bullets because they have a somewhat crude knurling.
Some cartridges in the box have longitudinal scratches in their cases, as if they had been put thru a die.