1.1"/75 caliber gun
1.1"/75 caliber gun is an anti-aircraft gun or artillery family.
Also recorded as 28 mm L/75 gun; 28L75.
In detail
It is associated with United States.
Sources
Each source is named with the standing the house places on it, so the evidence can be weighed rather than taken on trust.
reference work · Reputable secondary · Wikipedia
“1.1-inch/75-caliber gun”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q2400129: 1.1"/75 caliber gun
Consult the source