A Dictionary of Occupational Terms Based on the Classification of Occupations used in the Census of Population, 1921.
The printed volume is extremely rare: in the British Isles, copies are available in only three of the six legal deposit libraries, four university libraries, two public libraries, and the London Library. The UK National Archives has two copies, one in the document collection and one on the shelves in the Research & Enquiries Room. Copies occasionally surface in the second-hand book trade.
An electronic edition of the Dictionary, with an introductory essay by Alan Gillie, was published on CD-ROM in 1998. In this form, the Dictionary is presented as a single PDF file, with bookmarks for the individuals sections, but with no text search facility. Copies of this CD-ROM are held by the Society of Genealogists and no doubt many record offices and reference libraries. In March 2000 I published a review of it in Computers in Genealogy.
A digitisation of the Dictionary is available for online reading or download from the Internet Archive.