.600 Nitro Express
.600 Nitro Express is a rifle cartridge or Nitro Express.
In detail
It is associated with United Kingdom of Great Britain and Ireland. The record gives 1899 as its date of establishment or first appearance.
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
“.600 Nitro Express”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q4027910: .600 Nitro Express
Consult the source