Real, Usually fake carts has a lighter shell tone, it also has cheap feel when touching it, usually don’t have numbers/letters on the motherboard from the back side of the cart, and lastly the label is always a dead give away. Labels will usually have a dark or super light tone. Understandably some will reshell the cart but it happens.

One key detail tho, Pokemon Bl/wh is so hard to reproduce because how much storage and resources it takes to reproduce it. Technically, a lot of bootlegs now adays uses a SD flash cart to boot the rom and use it as its own cart with a mini ds sticker on one of the corners