I know you’re not supposed to clean coins, but…

Any suggestions for this bad boy? I picked it up metal detecting recently, and my curiosity is getting the better of me. I’m not trying to make money off it, just want to see if I can make out any identifying marks or a year. I’ve tried soap/water, baking soda/vinegar, WD40, and hydrogen peroxide. Is all hope lost? Any ideas out there?