Originally Posted by
mast3re
I've been fixing up this, what i presume is a Sekai 400 and was really interested in looking up the serial number but the guide doesn't quite line up for me. The serial number is Y3HC543. I'm not sure how original everything is but it's all looks period correct. would you be someone who could help point me in the right direction? the gearsets is made up of all Suntour - Honor back derailleur, Sprit front, LD 3000 stem friction shifters. Dia Compe brakes and levers. The levers have this part number on it 3403577.
Welcome to the forums. The 'C' is likely an incompletely struck '0' (zero), in which case the serial number format is consistent with Yamaguchi, a known Japanese contractor for Sekai bicycles. The serial number indicates it was manufactured during August of a year ending in '3'. Both the Honor and Spirt derailleurs were in production in both 1973 and 1983, but I don't recall seeing this Yamaguchi format on Sekai prior to 1980, so I'd be leaning to 1983 manufacture. August is in the grey region where it could be either a 1983 or 1984 model.