Hi I could be wrong but I don't think that's a proof. There was a proof set in 1939, it housed the coins in in a dark blue near black case. The silver coins were harder wearing then the later coins so they held more details.
Yours also has the same polished finish as my uncirculated 1955 half crown
it's nice to hear from a local 
Yours also has the same polished finish as my uncirculated 1955 half crown






















