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It is unaffected by your opponent's activated effects of Special Summoned monsters

This does not happen if a card effect pops it without flipping it or if it hits the Graveyard without being flipped in the first place

Id recommend this site to anybody who wants to proxy one or two cards

Mai, Scornful Striker Kambal, Consul of Allocation definitely used to see play in Vintage a long time ago, so the effect is solid, but this one is interesting because it's a two mana card as opposed to a three mana card, so it can be played in Lurrus

For a more accurate valuation, you can send your cards to a professional grading service like PSA or CSG