1980s Univega Competizione set up as a single speed with Jitensha/Nitto flat bars, a shade over 20 lbs but no clearance for more than 25mm tires:
1950 Raleigh Lenton Tourist w/ 3-speed Sturmey Archer hub w/ alloy shell, Weinmann concave 700c rims, Bluemels fenders, 32mm Paselas, 3ttt flat bars, alloy GB stem, around 25 lbs: