Just a bit of info on Schwinn Le Tours. They were one of the earliest Schwinn imports (Japan), and were a response to Schwinn's need for an affordable, lugged, lighter-weight-than-an-electroforged-Varsity/Continental "10 speed." The earliest Le Tours were built by Panasonic for Schwinn. If the bike in question is indeed a '73, I believe that's the first model year the Le Tour was offered. The Le Tour had quite a few incarnations over the years, including the Le Tour 12.2, introduced in '76 (main triangle 4130 chromoly, total bike weight 12.2 kilograms). Production of Le Tours by the end of the '70's began to go back and forth from Japan to the U.S. ('79 and '80 Le Tours were the only year models built in the Chicago Schwinn plant), and by '83 all Le Tours had full chromoly frames and were built at the new Schwinn plant in Greenville, Mississippi. By the mid '80's, Le Tours had evolved into pretty nice bikes IMO (which can be said of a lot of bike models).
I rode an '83 Le Tour Luxe nearly into the ground, having completely retrofitted it with all new parts at least three times. That frame hangs in the back of my shop these days. My teenaged son rode it a couple of years, it came time, more-or-less, for another rebuild, and he got a Surly Cross Check instead of sticking with the old Schwinn.