Steve very kindly sent me this picture of some Poles that look very similar to my own mystery variant of WN.13. They were genuine Hinton Hunt figures purchased in the 1970s as far as he remembers.
So the plot thickens because my own copy of the Hinton Hunt catalogue from around 1972 doesn’t mention this variant. This also rules out the possibility that they are Clayton figures because he didn’t produce figures until much later, and anyway I’m 99% certain that mine are not Clayton.
This leads me to conclude that the figure is either a genuine Hinton Hunt one (in which case I feel slightly sick about snipping off those plumes) or one produced by Der Kriegspielers in the USA. There is a listing in the DK catalogue 825-205 Polish Line Infantry Charging but no illustration of the figure.
Gentlemen the floor is open, please feel free to comment.