The Word “Beneficiado” means “made Good”, or “Has received the benefit of a review”…ie, Inspected and found to be sound.
Given that the German-made Ammo was made in 1937, finding the 1956 date and the “Beneficiado”, it is very probable to think that the ammo was about 20 years old, and as such was “inspected, tested and found to be serviceable” …(under most Armies’ rules for ordnance, or “Rule of Fives”, ammo is graded every five years of age, and by 15, is usually condemned to Surplus or Destruction…since this was “special” ammo, some leeway must have been given, following Inspection.
In Italian, the term is rarely used (Beneficiato) but means the same as in Spanish/Portuguese…Receiving a benefit, “Making Good” or approved.
It could simply mean “Repacked” ( ie, the external crate, after Inspection).
Since nearly all the records of AE and FNM have been destroyed when FNM closed (or “Was Closed”), the real connection between the word and the process which caused it to be applied is probably lost as well.
Another Histyorical Mystery which Cartridge collection brings us.