Original box is missing, but I believe this loco to be Hornby R261. 0-6-0 E2 Class Locomotive 104. OO gauge model steam locomotive. Southern Dark Green.
Hornby R261 OO Gauge SR Southern E2 Class 0-6-0T Steam Loco Green
Hornby R157 SR Class E2 0-6-0T Tank Locomotive 103 OO Gauge - Tested - Boxed
PHOTO SR CLASS E2 LOCO NO 2415 BR 32415
Hornby H203 Class E2 0-6-0 Dome Unpainted Green