The earliest reference I have for these outstanding hubs is in the Holdsworthy Bike Riders Aids for 1938, and the description there is as follows: "Cyclo - Unit Free Wheel Hub. In this latest introduction the freewheel is incorporated in the Hub. 12T. top cogs and 13T middle cogs can be obtained. In addition to this very important point it is claimed that the Unit has the following advantages. No loose ball bearings. Extra large pawls - strongest action - springs easily detached. Unit consists of hub with triple freewheel 12/- Stock sprocket sizes: Top 12-15T. Middle, 13-18T, Low, 17-21T Also in 2 speed. Top 13-15T. Normal 14-18T 11/-"
The hub was offered combined with Cycle 3 speed, Cyclo Poly, Cyclo Ace, or Witmy 2 speed derailleurs.
In the 1939 Bike Riders Aids, almost the same description appears, but this time headed Bayliss-Wiley Unit Hub Freewheel, and was also offered with the facility for a fixed sprocket on the other side.
In the 1949 Aids it is described as having large drilled flanges.
In the 1952 Aids it is also available with 4 sprockets
There is no reference to the unit hub in the 1955 Aids.
In addition to the Unit hubs made by Moyne already mentioned by Mick Butler, there was also a Simplex version.
Some would say that the Bayliss-Wiley unit, with its 4 rows of bearings, was over engineered, but I have never come across one with serious internal wear or with a failed freewheel. At some point there was a change to the axle used, and the earlier ones are not interchangeable with the later ones. Anyone with a lathe can adapt 4 x 3/32nd sprockets to fit the 3 x 1/8th sprocket version.
Peter Brown. Lincolnshire, England.