I believe this headstamp was not for the Italian military but rather a special headstamp made for Hamburg arms dealer Bruno “Benny” Spiro. Spiro sold more than 10,000 Italian Vetterli rifles (+1million rounds of ammunition) in 1913-early 1914 to the Ulster Volunteer Force (Irish Protestants). To the same buyer, he also sold 20,000 Mdl. 88 rifles and Mdl. 1904 Mannlicher rifles in 7.9mm. Un-headstamped 7.9mm cartridges are associated with this sale. Spiro also sold Vetterlis to the Irish Volunteers (Irish Catholics). There is an interesting article discussing pre-World War I Irish gun running activities and associated ammunition in ECRA #306 (Nov. 1990), English edition.
The article briefly discusses this headstamp but does not tell us who made the cartridge or what the letters “ES” mean. It could have been made at Capua. Perhaps the bunter was altered to differentiate between a military and this “commercial” contract. Considering its age and replacement by the 6.5mm rifle, were they even manufacturing 10.4mm ammunition at this facility just before World War I? Has anyone seen a 10.4mm Vetterli (not 6.5mm) manufactured at Capua with the “ES” inspector initials?
But then it could also have been produced by a commercial factory. dak21 mentions that the “primer is very flat” and is unlike those found on normal military Vetterlis. While a picture of the “ES” headstamp would be nice so as to know exactly what he means, the only 10.4mm Vetterli round I know of that has a “very flat” primer has no headstamp. Does anyone have another example of a “very flat” primer on a Vetterli?
And a final question for Pivi—What is the state of the ordnance records in the Italian military archives? Do they still exist?