This is what messicks told me. year built between 2006 to 2009
That's quite a range. I can take the mystery out of it.
Behind your battery is the VIN plate. In the "Product Identification No.", count the number of characters.
Older RTV's had a 16 character VIN. The 9th character is the year.
Newer RTV's have a 17 character VIN. The 10th character is the year.
BTW, all vehicles "should" have a 17 character VIN. (Kubota goofed on the early models but fixed it).
The 10th character/digit is always the year. On your car, motorcycle, boat... It's all the same.
In the past, they had used letters but that got confusing so I don't think they do that anymore.
It was confusing since you had to know the starting year for the alphabet and then they would skip letters like I and O because those looked like numbers so it was just a mess.