Originally Posted by
Machine Age
Serial number says 1977 according to vintage-trek but 710s weren't in the catalogs until 1978 and weren't listed with full 531 until 1980 so the exact year is a mystery.
(Most) any 7xx series bike is going to have a 531 main frame with 531 fork and stays.
There were a few 700 series bikes made with Columbus tubing. For some reason.
The naming convention is kind of simple until 1986; the 200, 300, 400 frames are all going to be either hi-ten and/or Japanese steel. 500 is going to be CrMo. 600 is going to be 531 main frame and fork and stays of CrMo or Manganese Alloy, 700 is 531/531 and 900 is Columbus.
There are a few very rare variances, but for the most part the rule holds true.
In 86 it went all nutty with mixing 531 main frame tubes with Tange CrMo... human sacrifice, dogs and cats living together- mass hysteria.