My father needs a damper for the back boiler in our fire place, but he does not know the name of boiler.?

The fire place was closed up for a number of years with an electric fire and just recently my father has removed this and started to lite the coal fire again.There was originally an all night burner in the fire place but this was removed and disposed off, and so was the damper plate in the back boiler Now he just uses an ordinary fire grate and fret, which is fine but he needs a damper to control the draft which in turn controls the back boiler.The problem is, he doesn't know the name of the back boiler.Is there any way of finding a damper to suit this.The name DUNHILL is in his head but he is not sure of this, was there such a make of back boiler.Someone told me the boiler is probably a GRANT or a GERCROSS. Where could i get a damper plate to suit.