I’m new to collecting diecast and was wondering if this is an error and if so how much is it worth
Ok so should I do an auction or a sellDifferent people call it different things but yes it can be classed as an error. I would call it a production error specifically. Most M2 collectors I know would leave it behind as they want perfection. But there are even M2 collectors who would want it for the '57 Chevy collections a unique piece to have. Since it is new - you can probably get a nice premium value (sold price) but over time it will not be worth to much more than a perfect casting.
We usually search the ebay sold listings to get a current market value. Whatever you see today at ebay will trend down over the next few weeks (most of the time) for most M2s. I also filter for US only listings.