The geometry and frame materials are normally given in the brochure for that year.Many thanks to the people who have contributed significant information to the site.The long chainstays, 47cm, provide heel clearance for the rear panniers, and contribute to a comfortable ride.These frames and bikes are still highly sought after by knowledgeable tourists.The steel racing Treks will never again be used by top racers for racing.However, the 720 will be used (and coveted) by experienced tourists well into the future. Expert framebuilders John Thompson, Rick Faultersack, and Kelly Gamble built them.This longevity and popularity has raised the value of this bike over similarly-priced vintage Treks of the period.Two parameters are specially important to the 520 over the years: chainstay length (as pointed out by Robert Cooke) and the type of brakes used.
Additionally, the table of Trek models by year includes all Trek bikes through 2005.
There also are four early price lists from bike shops in Santa Barbara, CA.
The price list and values page also has a list of bike prices when new.
The Columbus tubing, racing geometry, and fastback seat stays were characteristic of this model (not to be confused with the later bikes from the mid-80s having cast socketed seat lugs in fastback form).
Another special feature is the three holes, of increasing size, in the top of the seat lugs and head lugs.
An exception is the TX900 which has no cast-in "TREK".