I tried Googling "Spear Point Seat Stay", and the only builders I saw referenced that actually had anything remotely similar to what was shown were Flying Scot, Hetchins, and Holdsworth I saw reference to EKLA lugset which Flying Scot was purported to use. The spear point had that similarity, but was otherwise quite different in the lugs.

Holdsworth and Hetchins (Vade Mecum and Nulli Secundus) pictures show more fantastical lug cuttings, and I might find that plausible, however the seatstay spears illustrated at the site for Holdsworth are quite different.

I had fun attempting to research, but I can't say that I have reached any definitive conclusion.