50's Nervex Frame ID unusual rear brake bridge

[MrJustin72]

Trying to ID an English thread Nervex pro frame, early style with horns. Had frame for a year now but still no positive ID. Frame number 5349 with 56 stamped at right angles. The rear brake bridge could help? Never seen another frame with same braze on in the centre of the bridge. Could have been rebuilt at some point as the headache holes have been bronze welded over añd another set of serial numbers stamped on BB L62103.