I remember vaguely something about reversers in Hawker Hunter fighters...
Early 1950s... they experimented the use of T/Rs on that type.
But I cannot recall for airliners, when they appeared.
Comet
IV - two engines could be put in reverse...
Caravelles - only appeared on Caravelle
VI-R and subsequent models.
And the 707s or DC8s had reversers from the first production models.
xxx
Happy contrails
(s) Skipper