Paperback imprint of John Spencer & Co. London until about 1967. Published an awful lot of Lionel Fanthorpe under MANY pseudonyms.
This Eye-Melting Gallery of covers covers most, if not all, of the Fanthorpe Badger works: there are still some books by other authors left to find though. John Glasby might well be responsible for much of the rest.
The "#SF" serial numbers are fairly clearly books: the "#SN" serial numbers for magazines are a bit more questionable. "Supernatural Stories" was used for collections of shorter fiction, "Supernatural Special"s fit into the same sequence but only contained one Novel in each. It may well be easier to convert all the "#SN" pubs into Anthologies and Novels (maybe "Collections" when Fanthorpe wrote the entire issue).