Interesting coin @Shea19! I really like the "reverse" with both sides of the coin clearly visible. Like you, I don't collect error coins but I think I'd also have been tempted to add that to my collection if I'd seen it. I have a double strike as well, albeit not a flip-over like yours. The obverse of this Gallienus is double struck, but the two strikes are aligned at quite a close angle. This results in an evenly spaced obverse legend of GALLIENVSS AVG - with an extra S, and a big chunk has been taken out of Gallienus's neck. You can see evidence of the double strike most clearly around his nose and chin.