These pannier sets were after market items made after the war for fitment to any machine...Thus the multiplicity of mounting holes..Perhaps due to the ready availability of ex WD pannier bags they appear to have been made so that those fit pretty well dimensionally...They were finished in either black or maroon and were pretty common on the jumble circuit in the UK for many years...I bought a new, boxed set about 10 years ago from a chap who had about 15 sets..They originally came with webbing straps that had cadmium plated fittings...Two single straps for each pannier, not WD type 'Y' straps...You can see the attachment points for these straps
They currently live on my 'Indian takeaway' Royal Enfield that I use as a daily hack...This pic. was taken about 4-5 years back when I first fitted them...Ian
email (option): ian@wright52.plus.com