The HSS appears "laid on"
(eBay item 232546236533 sold for 14 quid, 02 Nov, 2017)
Laminated HSS parallel plane iron by F. Mountford & Sons, Sheffield (edge tool makers taken over by Tyzack in the 1950's). 2 1/4" wide, 7" long, approx. 5/32" (4mm) thick, 1 3/16" of life left. Very good clean...