Record Cards from 37506 whilst based at Cardiff Canton TMD (CF).
These records date from 1985 - Last Classified Overhaul 27th March 1985 (Crewe Works).
37506 (D6707 37007 37506 37604) Is currently in service with DRS under the guise of 37604. More Information can be found here - C37LG - 37604

More information can be found here Wikipedia - BR Class 37  -  Class 37 Locomotive Group - Preserved-Diesels Website