I'm pretty sure it is for msx as I was able to count what seemed like 25 pins on one side of the edge connector, and it has the telltale hole on one side of the cart that MSX carts often have, so I would argue that it is msx, and that the edge connector seems to be too long because the cart is actually shorter then what we are used to. In Brazil the MSX machines had many non-standard features, so it's possible that the cart slot that this cart was made for carried the same number of pins, but was not as wide. Brazil is notorious for boots for just about every system of that era, so that's what this probably is, a boot for a non-standard Brazilian MSX
Hmm, bizarre, perhaps for one of the zillions of Brazilian Famicom/NES clones, it doesn't look like any nes or famicom cart I have, and I have hundreds, originals and boots.
@manuel:
I've seen one or two that used things like flatcable connectors for their expansion bus and other strange things. I had never seen one with an edge connector that was non-standard before, I was just throwing ideas out, as I know that some Brazilian machines didn't follow the standard closely.