Well the SN say that should be a 22inch 82 720. Course the 720 was not a complete bike for 82 model. That said I have found errors in their SN database before. LOL
I think you have a 82 728 that got some nice upgrades along the way. The rest of the bike looks correct. Center pull Gran Compe 450 center pulls. Huret Doupar did come on the 728. 83 720 went to Canti.

http://www.vintage-trek.com/images/trek/Trek3.pdf