John RR, I think you are right on that. On the date on the tires these are narrow tread bias belted tires and if I am remembering correctly I haven't seen these type tires sold in about 20 years. Here are the pics.
I called Dexter and these rims went out of production in 1980 (gee ain't I lucky ! ! ! !) so these could be the 70s????
I am figuring now from what I am seeing 195X75RX14 is what will come close to this size wise. Eventually all four tires will have to be replaced.
The above rims came in 13", 14" and 15". One thing for sure if I get new ones I will fabricate covers for them so the sun won't kill them.
Funny I have a military cargo trailer designed for pulling behind a tractor in train fashion (front axle steers) and I have had it over 10 years sitting outside and the tires are not cracked at all as they have the additive. I suspect this trailer was made in the 80s.
It is for sure the companies don't want to add 20 cents a tire to put in the additive to make them last as mulitplied over millions of tires cuts into their profits.
One of the sites I read says the ten year date code was designated because they figure tires won't last over ten years and it is for sure they don't want them to.