You are buying a used Mercian Touring/Road Bike.
Beautiful British Racing Green finish and custom cut lug work. Was originally ordered as a custom build and retains the majority of the original components (original sales receipt included from 1980). Not sure on the exact model and unfortunately the sales receipt does not state which frame model was ordered. It does not appear to be a Mercian dedicated touring model which was the King Of Mercia-Touring, as it does not bear the heart cutouts in the lugs. Made in Derby England! From catalog references it appears that Mercian almost solely worked with Reynolds 531 double butted tubing, so it's fairly safe to assume that this was constructed with such unless this was a 753 Special (which used Reynolds 753 tubing).
57cm Top Tube (center to center).
57cm Seat Tube (center to center).
Brooks Professional Brown Leather Saddle.
SR Laprade Fluted Seat Post.
Cinelli 1A Stem (90mm).
Cinelli Campione Del Mondo Handlebar (44cm outside to outside).
Zeus Gran Sport Headset.
Shimano Exage Brake Levers.
Gran-Compe Brake Calipers.
Huret Success Shifters.
Huret Success Front Derailleur.
Huret Duopar Rear Derailleur.
Stronglight 99 Triple Crankset (170mm, 28/42/48 Chainring combination).
Phil Wood Bottom Bracket.
Campagnolo Superleggeri Pedals with Christophe Toe Clips and Christophe Leather toe straps.
Phil Wood Hubs laced to Mavic Module 27 x 1 1/4 Rims.