3 inch/50 caliber gun
3 inch/50 caliber gun is a naval artillery or rifled breech loader.
Also recorded as 127 mm L/50 gun; 3-inch/50-caliber gun.
Overview
American naval artillery.
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
“3-inch/50-caliber gun”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q4634025: 3 inch/50 caliber gun
Consult the source