John — All fish are Murano, aren't they? At least a browse around eBay would lead you to that conclusion!
This beauty was made by Nazeing Glass Works of Broxbourne, Hertfordshire, and sold wholesale by George Davidson of Gateshead, appearing alongside fishing floats made by Nazeing in Davidson's 1961 trade catalogue. I don't know why this arrangement was made between the two companies, but I suspect that Nazeing did not then have an effective wholesale distribution network for retail fancy goods, having ceased production of cloudy glass in the 1950s, so it made sense to add them to the Davidson product range.
Nazeing fish have two distinct characteristics distinguishing them from Murano fish. The tail is a split continuation of the body, retaining the body colours, rather than an applied tail. The other is the applied dorsal fin, drawn up into a series of points, usually numbering between about four and seven.
They're fairly consistent in shape, but vary considerably in size. They come in every wonderful colour and colour combination you could envisage, plus some that you wouldn't have thought of.
Note that your fish is slightly unusual as it has a coloured eye — only the second time I have seen a coloured eye. Coloured fins are also an unusual variant.
I just love them, and, if we had the space, they would be my first choice of any type of glass for a collection.
Just one mystery remains for me. The name of the inspired master glassmaker who made them.
Bernard C.

Sources:
Timberlake, Geoff, Nazeing Glass Works, 2003Stewart, Chris & Val, Davidson Glass — a history, 2005