Hiya,
I'll add a few:
* The "key" is a toggle switch or 2 wires you twist together
* The starter switch is separate from the ignition switch and actually a salvaged foot starter switch from a 1957 Chevrolet Apache mounted in "the dash".
* The distributor has "spark ******" setting for ease of starting by hand.
* No instrumentation of any kind, you use your ears and the seat of your pants to set the throttle.
* Nothing is made from plastic, iron and steel only.
*Aluminum was still "new and untested" as a component.
* Liquid cooling was still a relatively new idea.
* Chain drive was still offered as an option.
* Everything on it was made in the USA by a person running a machine, not CNC.
* There are no warning stickers of any type and nothing is labeled as to it's function.
* It has either a crank handle ratchet or a rope pulley to turn it over by hand as electric start was still a "newfangled idea" when it was made.
* It has more than one transmission.
* The transportation museum calls you at least once a year and asks if they can use it for their "early 20th century industrial machine" exhibit
* All the nuts and bolts have square heads.
* Not a Phillips head screw anywhere, straight head only.
* It has "poured" bearings
* There are web sites, newsgroups and magazines dedicated "to the preservation and continued use of the American classic <Insert tractor name here> tractor"
* Most of your living and some of your dead relatives learned how to operate a tractor on it.
OK, that's it for now.
Tom