This is certainly an old thread, but just to add to the store of reliable information, I have a 48-key Boyd Wheatstone treble SN 23697 (confirmed by Colin Dipper and Wim Wakker) with 2 air levers. Its leather case disintegrated but not before I extracted the black oval label with gold lettering, stating
HARRY BOYD
DIRECT IMPORTER
AND
DEALER IN EVERY STYLE OF MUSICAL INSTRUMENT
WHOLESALE AND RETAIL
20, NEW BRIDGE STREET
NEWCASTLE-ON-TYNE