This is the British Slinger that first appeared in the Miniature Figurines 72/73 catalogue as PB 157.
Both PB ranges were based on Phil Barker's books Armies of the Macedonian and Punic Wars and The Armies and Enemies of Imperial Rome. This figure is taken from illustration 57 in the first edition of AEIR.
The code numbers for the AEIR range correspond to the illustrations in the book plus '100', i.e. illustration 1 is figure 101.
The base is stamped PB 157 on the upper surface in the usual manner.
Whilst it's nice to see a slinger posed doing something other than slinging this chap does tend to look rather odd when lined up next to his fellows. Nice early 70s rock band haircut though. He would - of course - make a perfectly good Celt or German and more besides.
I struggled to strip the paint from this figure and have left it as you see it - with traces of stubbornness defiant despite all my efforts.