Hi Allen
The Country Gentleman Association ran from 1893 to 1975,after that period it changed its name, and was still running in the 1980’s,in the latter years it moved from Letchworth to Eaton Square London, I think no 19 from memory, they shared a building with the Institute of Psychiatry, at the time I was visiting every day (As a courier, nothing else)
They produced many books over the years, the one to shy away from is their calendar book as it does not have any decent references.
I have a complete run of original copies, but a little warning the late 1920’s copies to the 1930’s can make eye watering sums
Hope this helps
Mr Wallingfield