obvious bootlegs do not use circuit boards that say SNK or SNK Playmore
http://mvs.gotwalls.com/index.php/Main_Pagethe way you know if a MVS cart is a bootleg is by comparing it to the original photos in that link. be aware there are variants and often times those different version are shown on the scans page but it may not.
if it doesn't match it may be a bootleg but not necessarily. it could simply be a repaired original by SNK or 3rd party.
but i think most of the chips are toshiba or sharp so that may be a giveaway.
it is not uncommon for SNK themselves to repair a board and put programmable chips in though, so that's not a exact way of determining.
often times a dead giveaway is when the solder is not perfect on the back of the board.
also some games had a SNK warranty seal so you can tell if it hasn't been tampered with that it is all original,
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http://www.rareneogeogames.com/wp-content/uploads/2014/06/-1711552615132880041.jpg
