WW2 period British 1922 pattern other ranks khaki wool Service Dress Cap, the Cap Britain went to war in, in 1939.
The Cap has a brass G V1 R Royal Army Service Corps cap badge and one brass general service button (one missing). Below the cap badge sits the leather chinstrap. Inside, the sweatband is in leather.
Overall condition is very good, the cloth free from moth holes but with a small amount of surface wear just above where the missing right chinstrap button would sit.
There are no size or date markings I can find.