S. Tyzack & Sons of 341, 343 & 345 Old Street, Shoreditch, London were a large retail mail-order company. Established in 1843, they not only supplied a vast range of engineering equipment, but also common household goods of all descriptions. Of the lathes they offered the best-known was the Zyto, a machine that can be traced back to a 1926 Model Engineering Exhibition advertisement for the Billing Tool Company of 101 Clerkenwell Road, London, who offered a range of items for the model engineer including bench drills, 3-jaw chucks and a fast-and-loose-pulley driven Universal Sawing, Boring and Grinding Machine. However, their most important product was the B.T.C. "Supreme", a simple little  3" x 12" gap-bed, backgeared and screwcutting lathe with a full-nut leadscrew, dog-clutch and a single swivelling (but distinctively T-slotted) tool slide. In 1927 Tyzack took a stand at the same exhibition and, obviously seeing some potential in the design,  announced the acquisition of the Billing company and the re-branding of the B.T.C. Supreme as the "Zyto". The machine was described as "The latest all-British Production" and available for £7 : 16 : 6d, exactly one shilling less than Billing's price the previous year.
All Tyzack lathes had something of a dubious pedigree and the little plain-turning, 1 5/8"  x 5.5" gap-bed Model F was no exception, the actual manufacturer being Flexispeed in Sheffield. Advertised for a short time during the late 1940s, this, the most basic of the Company's models, was equipped with a square-thread leadscrew, the ordinary machine selling at £7 : 8s : 6d including post. As an option the Model F Super could be ordered at £9 : 8s :6d; this included the Flexispeed patented self-acting traverse - a two-stage reduction by worm-and-wheel gearing.
Just a single, swivelling top slide was fitted with a simple triangular-plate toolpost. As Flexispeed also listed the fitting of backgear and a compound slide rest, it's likely that the Tyzack version might also have been available with these desirable extras.
Further details of this lathe can be found in the Flexispeed section of the Archive.