The Stovebolt Site Forums The Parking Lot Big Bolts Air Brake endorsement

This topic is very interesting... I have air brakes on my 1945 GMC COE and don't have and never have had to have a CDL or air brake indorsement. I have 'Farm tags' on it and it has always been licensed that way. I use it to haul my D4 cat and have crossed the scales carrying 36,000 lbs. of green myrtle wood logs. The weighmasters only concern was as to whether my tires would hold the weight. I've always contacted the Farm Bureau, local DMV and have shown the truck to many weighmasters and State Police, all of them have never mentioned anything special about having an 'air brake indorsement'. My COE is set up as a flat bed with beavertail and also as a tractor to pull a trailer with air brakes. The only thing about 'Farm tags' is I can't haul anything for hire. Can someone point me to the Federal law that is being talked about? I live in Oregon and have never heard of this.