This is the advice i've given to others, but i've never used this method on a nickel as far gone as yours. This might be worth a shot. Soak it in Worcestershire sauce over for a few hours, flip and repeat. wash sauce off between flips, and then dry. Leave it alone after that. no matter what else you read about dremels or CLR or anything else, the best your nickel will look is after soaking it in Worcestershire sauce. What it does is take the reddish color off and leave it a dull gray nickel (revealing dates sometimes). Throw it in a 2x2 flip and enjoy it the way it is. I've ruined far too many buffalo and v-nickels chasing the look others claim to get from cleaning. I'm not saying that they lied, i'm just saying that for 90% of nickels the remedies do not work for.