The original (1917) is lost. There are more authorised replicas than four (I think 16). The one in Tate is the Milan version from 1964[0]. Tate owns the one numbered "2/8". I don't know which other Tate should own, the known versions are all somewhere else. I don't see a single reason why they would sit quietly on an unknown version just for "accidents".

[0]: There are 13 of them: 8 regular, 2 for museums, 2 proofs, 1 prototype (which was not listed officially at that time). Apparently they made at least four other unsigned replicas at that time under the direction of Duchamp.

Source?