Hi Mog, Thanks for this.
I did find them in a couple of Trade Directories, but they didn't say much...
Entry in Billings Directory of Devon - 1857 - "Martin, T. Engraver, Wolborough St" & "Engraver - Martin, Thomas, Wolborough St. (Ref: Westcountry Studies Library)
Slater's (Late Pigot & Co) Royal National and Commercial Directory - Newton Abbot - 1852-3 - "Tornographic Seal Engraver - Martin, Thomas, Courtenay St. (Ref: Westcountry Studies Library)
It looks like they were early adopters of new technology and then seals went out of use, maybe? They used Tornographic in the earlier one, but just said Engravers in the later one. They were still saying that they were Tornographers in the 1891 and 1901 census, but maybe they were just using it as a clever word for Engravers.
Thanks for finding the above.
nick