J. Thibouville-Lamy & Co. were a firm that was established in Paris in 1790 and opened an office in 10 Charterhouse Street, London, in 1880. 

In France they were manufacturers of every type of brass and wood instrument, who advertised their extensive "steam factories at Grenelle, La Couture and Mirecourt." At the latter they made a wide range of Guitars, Mandolins and Ukuleles. Soon after they opened their London house they added Banjos in their catalogue but these were made for them by British makers like George Houghton & Sons. The majority of the instruments sold under their name, including Ukuleles, were made in their own factories in France but not Banjos and Banjoleles. (it also appears likely that they were the OEM for some Ukuleles to be distributed by some of the UK firms?)

Jetel was probably their biggest brand name and they used in on a lot of chordophones including Ukuleles, (made in France and possibly Spain or Italy?), and Banjoleles, (made by GH&S), I have also seen them use Jetelele on some of the most basic models but they usually just assigned a number to signify the level of decoration the 8 was the fanciest. Victory and Lamy are other brand names that I have seen them use, again on GH&S Banjoleles and I suspect them of being JTC-L and having something to do with Down Souths and Handels but I have no firm proof? They also produced a line of Ukuleles called Virtuosa in the 1930's.

J.T.C. - L.

This is the company name in small letters on Down South and Handel branded Banjoleles but I have no idea what the letters stand for. They were also the company that imported Carlo Ricordo Ukuleles from Italy(?) to the UK.

I have heard that it was based somewhere in Sussex, England. but with the lack of information I have it could be some derivation of J. Thibouville-Lamy & Co. trying to appear less French?