Were Tachographs used in trucking in the US?

Yep. Long time ago.

Wagner Sagnamo comes to mind, off hand. Sure there where many other manufacturers.

Had combined speedometer, odometer & clock.

Saw a Sagnamo still mounted in an old, old truck when I worked at a truck stop back in the 80's & was fascinated by it. Some others in a few other trucks.

 

1979 Peterbilt 359 with one.

 

Yes. In 1989 I drove a 1986 R Model Mack. It had a Tacograph built into the dash, it was a speedometer and a clock.

 

I have no idea.

 

weren't they called tattle tails back in the day??

 

Yes.
And guys would change the gear so that they would read slower than actual speed and time, or stick a cigarette filter in them, or….
Moral of the story.
Try to create hours of service, and ways to track it, and we’ll find a way to jack with it.

 

I also drove an R Model with one I didn't use it though.