DOT CODE WITH LETTERS

I believe that is manufacturer and plant number not the dayte code.

Look on the other side of the tire

DOT date code is # s like 4912 , meaning 4 th week Sep. 2012.
Prior to. 2000 it would have been 3 #, week mo last digit. of year.
A bias ply spare on my boat trailer made in '86 dated to '1985.or even to 1975.when date codes began. found and changed that last year.
Since that tire was a E 78/ 14 bias ply with code of 466 , all info points to it being a 1976 maybe '86 tire. The E 78/14 sizing says 1970s. By the mid '80s sizing metric proportions and percentage were dominant.
A new trailer doas not mean new tires. They could be years old

I believe a date code of 4912 would mean the tire was made the 49th week of 2012.

Yes, 4th week would be 0412.

The DOT code is a 10 to 13 digit "number" on the sidewall of every tire that hits the street in the US.

I go into more detail here: http://barrystiretech.com/dotcoding.html

The complete DOT code only needs to be on one side, but a partial code is required for the other side - and that one will be 6 to 9 digits long.

Tires that do not hit the street are NOT required to have a DOT code, but many do, and they are NOT required to follow the DOT coding format. Sometimes the tire manufacturer will have its own coding system - as did even street tires prior to the early 1970's.

Frequently if the tire has the date code only on one side of the tire , tire jockeys and tire shops will turn that tire to the inside of the wheel.

rx2tee wrote:
I just looked at a friend's trailer and the DOT code was R2NN.

DATE code and DOT code are two different numbers.

Note your original post says "DOT Code", which is exactly what the code you found is. It's not the DATE code.