280 mm mortar M1939
280 mm mortar M1939 is a siege mortar or artillery model.
Overview
Heavy mortar.
In detail
It is associated with Soviet Union.
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
“280 mm mortar M1939 (Br-5)”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q2042997: 280 mm mortar M1939
Consult the source