Bofors 57 mm Mk.1 gun
Bofors 57 mm Mk.1 gun is a naval artillery or autocannon.
Overview
1971 Swedish naval artillery.
In detail
It is associated with Sweden.
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
“Bofors 57 mm Naval Automatic Gun L/70”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q14905318: Bofors 57 mm Mk.1 gun
Consult the source