21 cm Mrs 16
21 cm Mrs 16 is a field howitzer or howitzer.
Also recorded as 21cm Howitzer.
In detail
It is associated with German Empire.
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
“21 cm Mörser 16”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q212917: 21 cm Mrs 16
Consult the source