Hello again!
Many thanks for all the help identifying the damper and as a result, I have just got hold of a John Grey damper which seems to do the job perfectly.
I came about as a result of my collection of a JG Autocrat 14x5 COB - what a beauty! - and the seller had a JG Autocrat 14x5 wood shell - without lugs - but with a damper (and blue rectangular badge) - which they wished to get rid of.
You can see from the 'installation' pic that there were quite a few holes drilled into the shell to accommodate both the Carton as well as the original damper.
So it seems the leatherette is a definite no-no, also according to the vendor of both the above - so - Arctic Oyster? Purple Diamond?