A bit of information I have learned: The Trek 3700 has a freewheel. Oddly numbered - TZ37 - with the TZ designation indicting a Freewheel.
Confusing as the Trek data sheet for the 3700 specs the Cassette as a TZ37 which googles to:

"The Shimano TZ37 is a freewheel. It's a more basic type of rear gear system, often found on entry-level bikes."

Not a limiting factor for what I intend to do with the bike.