Low number places it as an early 60's Holdsworthy Claud.

Wonder which Nervex lugs it has? Serie Legere were on Coureur and Olympic while Nervex Pro was on Cordon Bleu which seems to be the more common frame one runs into these days.

Perhaps you have but if you look at early 60's Claud catalogues on nkilgariff.com you should be able to sort it out.

As Juvela says really can't take any further without pics. Looking forward to seeing details!