1950s Holdsworth track frame in original paint with horizontal dropouts and chain tugs, nice wrap over rear stays (as used on their pro frames) and elegant Nervex Professional lugs, 56cm seat tube. Wheels Weinmann rims and Airlite hubs, rear flip flop hub with 2 fixed sprockets. Milremo crankset. Brooks B17 saddle. Lyotard Quill pedals. GB brake levers, bars and stem. Brakes GB Courier Plus which date the bike to early 1950s 

https://www.classiclightweights.co.uk/classic_designs/g-b-brakes/