English Electric Type 1 (Class 20) Locomotives D8000 - D8127 (20001 - 20127)
 Drivers Standard Preparation and Disposal Duties for Type 1 Diesel Electric Locomotives E.E.Co 1000 H.P. Nos D8000 - Onwards
Issued April 1961   -   BR33003/212.

More information can be found here Wikipedia - Class 20  Class 20 Locomotive Society