I’m kinda thinking along these lines.
The letter O was skipped being used on Fender tags and on VINs to reduce confusion. The number 0 was used in its place. Like shown in a previous post, O= Super Stock. I thinking because the letter O was not used on vins and fender tags they substituted the letter O with the number 0 BUT the number 0 is representing the letter O. What do you all think?