Sometimes we're nice and put a FatBoy sticker on the underside of the pickup, but it's not 100% of the time. The only way to tell for sure is to check how wide the magnet is inside with either the paper and iron filings trick (don't do this while it's mounted on the bass) or with the magnetic paper to peek inside. The FatBoy will reach almost to the top and bottom edge, the AXY will be in the center and half the width.
A FatBoy and a standard AXY should sound the same with the pickup mounted either direction. We could make an AXY pickup with the coil cast toward the top edge of the pickup making the actual pickup part about 1/4 farther away from the bridge without changing the routing. Anything more dramatic would need more dramatic modification.