parkmanaa you might be on to something.
My spare is almost 10 years old. Code date is 0308 and is a Mission Tire, not a GY Marathon. I have no clue who makes Mission tires. I bought the 5er new and never paid any attention to what brand it was, just assumed it was a Marathon as that was what was on it. I just added air if needed over the years as it was under the trailer and dark and enuf pain in the butt just to get air in the tire.
Keystone must of had a pile of mission tires in a warehouse somewhere and just used them as spares. Probably cheaper...
The tire they brought to replace my second blow out is an Advant. Never heard of them either. But along I-75 on a Friday night at 10 o'clock on a holiday weekend I would have taken a wooden wheel off of a Conestoga Wagon if it would fit.....