US90 questions

[firehart]

I just picked up this US90 and I'd like to know what year it is. Are all three tires the same or are the rear tires different? They are look alike and are the same size. The serial #US90 203586

[firehart]

I see the difference in the tires now and I think its a 73.

[Vealmonkey]

The front tire is supposed to be a ribbed tire with the ribs running front to back. The current front tire in the picture is what the rear tires are.