British Single breasted Greatcoat.
This model was first issued in WW1, then continued to be used by the BEF in 1939 at Dunkirk and throughout WW2 mainly then by home guard etc.
The model 1909 was to be replaced by the 1939 double breasted model and issued to the BEF but many units were still wearing the 1939 and pictures of troops at Dunkirk waiting to be evacuated.
Model 1909
Rifle patches on shoulders
Watch pocket
Mad of Wool
rear belt with 3 GS buttons
Sized to fit over your tunic