These are subsonic cartridges loaded in small quantity for the firearms manufacturer Star Bonifacio Echevarría, S. A., the well known pistol and submachinegun maker.
The cartridges were identified by the lack of headstamp and were loaded in 1980 according to the box. It seems that the boxes were identified by a hand written cross in the front and in the back. The boxes were commercial.
According to additions made by Alfonso Orea to his 1992 book Cartuchería Española, this cartridge was loaded with a 11,50 g (177 grain) bullet, and the complete cartridge would weigh 16 grams. But such a heavy bullet would be too long for this caliber. I have pulled one bullet and it is a conventional brass-jacketed 7,5 gram one (115 grains). The cartridge weighs 11,75 grams.
The primer has three very faint stakes and a red seal, but the shade of red is darker than the one used in curren production cartridges. The three stakes are an unusual feature too in Toledo 9 x 19 production.