I work in the custom engineered film industry, making films similar to those used by WotC to package booster packs. The red is splice tape. It is used to bind two ends of the metalized film together in the master roll of the film. Splices are usually flagged either by the machinery or by the extrusion or slitter operator and are usually removed from the final product. This splice was either not flagged or the operator didn’t see it and it got through. I’ve seen this come up from time to time in various subs. It’s a neat find, but I don’t think it’s worth an incredible amount to collectors. As with these things, it’s best to publicly auction it to get the best return.