The Hayman Company was formed in 1969 when Jim Burns and Ivor Arbiter went into partnership. Also involved was Bob Pearson from Vox (designer of the Phantom range) and two former Burns colleagues, Jack Golder and Norman Holder, who took care of the woodworking and truss rod engineering.
Hayman produced three guitar designs but the 4040 was the only bass. These basses were good to play however, and produced sounds somewhere between a P-Bass and a Rickenbacker. Each Superflux pickup had eight adjustable screw pole pieces so it was easy to balance the output from the strings, and they benefited from the hidden 'Vibrasonic chamber' beneath. Joint string trees neatly feed the strings from nut to tuners.
The bridge was a curious affair with a clear Perspex anchor and the steel saddles on a separate plate. The slab body had minimal curving to the body edge front and back and the overall shape is similar to the early Wal Pro basses that would appear a little later on. The neck was fixed using a standard 4-bolt plate with a separate chromed plate displaying the serial number. Lefties were made to order. The company morphed into Shergold, controlled by Golder and Holder, after Jim Burns pulled out.
The confusion as to when production finished is due to their serial numbering system, which suggests some Hayman basses appeared in 1975. The Hayman brand name was applied to instruments distributed by Dallas Arbiter until termination of the contract in 1975. From 1975 to 1982 their guitars and basses appeared under their own 'Shergold' brand.
In short, the Hayman 4040 and Shergold Marathon basses are very good indeed.
I owned a Hayman 4040, sold it, regretted it. I also had a Shergold Marathon, sold it, regretted it.