They first appeared in 75, which is the year of the Greig picture, and the first year of the original GN Scoop. (I think the picture was taken at the World Cup Semi Final at Leeds, the bowler is Gary Gilmour) As Greig became England captain later that year, the gloves got a lot of publicity. They lasted until about 79 / 80 when SP went bust. Other players to use them included Ian Botham, Rodney Marsh and Clive Lloyd.
The design had individual fingers but a one piece back. Other manufacturers had similar designs but had to make sure that their design did not infringe SP's registered design. The people who had similar designs were Duncan Fearnley, Morrants and Stuart Surridge. GM had a one piece back design, but in was shaped to have separate fingers.
In 1980, the SP gloves sold for £13 for the top of the range leather palmed version.