I can't shed any light on the braze-ons. But I do have some more questions. The 3 braze ons on the seat tube side of the seat stays are strange, two on the drive side, not for mudguards as there are already eyes on the drop outs.
As you may remember Mark, I have a 1952 Gillott Connoisseur (which I am STILL restoring!-the above Gnutti/Magistroni set up is perhaps the final piece). Mine #522851 does not have the serial number braze on nor the headtube grease port and the windows in my lugs are perhaps slightly smaller although your black painted lugs may just appear slimmer (I've heard it's a slimming colour):-) Do you think the gear hanger has been modified by Gillotts or at a later date? My Connoisseur has the same Agrati forged ends but with an off-set Simplex hanger which is forged as part of th D/O, it also has a double roller on the drive side BB for a simplex Juy 53 but no braze-on for the mech itself. Are the forks original? Mine has the RJB fork crown (I have a pair of forks from a 30's Maclean with that same fork crown). And finally is the stem a Titan or the Gillott branded one that is very similar? and do you know it to be original equipment?
Very nice bike. But the '52 pursuit is still the one i covet.
Simon Bird
London
England