A box of 12,7x76 mm (.50 Spotter-Tracer) rounds from the Palencia factory of the Santa Bárbara company. Its purpose was saving on the expensive spotter-tracer bullet. It was probably an export contract, as suggested by the “Made in Spain” caption.
The T249E2 designation suggests that this was an US experimental cartridge. Was it ever adopted and given a “M” number?
The first cartridges in this caliber loaded at Palencia used US cases, mainly from Twin Cities. In 1972 they started headstamping with M48A1, regardless of bullet type, and they did so it since then.