Didn't find the serial number inside as I had hoped so will have to search for the plate.
There was L28 and R28 on the reed pans not sure if this has any relation to the model or serial number, or perhaps a batch number?
Not much on the web about H. Boyd but found this:-
http://banjolin.co.uk/folkipedia/index.php?pageName=Boyd
Might be of interest to those who haven't already found it.
Don