Vintage T-Shirt Forum & Community Authentication Appraisals

Could someone please help me value this T-shirt for selling made by SJM
Good condition, no broken stitches
Brought yesterday in a charity shop gently faded
Any help will be a bonus as I haven’t got a clue

The OG 70s War is Over shirts, have been getting the $500 recently, they seem to be on an upswing, maybe yours could ride that wave and get more - but would say $100-200.