... that's odd, have you had the vernier gauge out?
I think it's late 50s but I'm not sure, the chap I bought it from had it sold to him many years ago as a Pratt. But those are defo Fleur De Lys lugs that Gillott used. Got a stamp on the non drive track end, but doesn't sit in line with Gillott style of stamps from what I can see. Shall strip a couple bits at the weekend and see what that reveals.