This plate requires a mathematical explanation. It belongs to Duane Bollenbacher, retired math teacher, and here's the very short explanation:

"The Ohio Council of Teachers of Mathematics (OCTM) was organized and had its first-ever conference in the spring of 1951 - hence "51."

Luther Shelter is the only living charter member of OCTM. Duane joined in the 1960s. Duane says he has a photo taken way back in 2002 of the license plate with Luther and Duane. That photo is on the OCTM website.

If you have 15 minutes ask Duane for the longer version.