The Sheffield S20 was manufactured by Sheffield Radio Ltd in about 1936.
6-valve dual-wave set. Model code believed to be correct. Age is based on station ID's on the dial:
Absent, 1ZH ceased 1935
Absent 2ZB, 4ZB started 1937
Present 3XL, 4YO started 1934.
Original construction is quite crude, showing how far Sheffield came as a company to their well constructed and tidy sets in the 40's. Dial looks like two paint tin lids.
Photos and restoration by Tim Sanders.
Chassis Notes (most schematics can be clicked to download a full size version):