If you can get to the backside of the hubcap, the centre retainer of the three pins is held onto the back of the barrel with what looks like a rivet. It is, in fact , a screw...if you can somehow put a slot in it [dremel?] you'll be able to simply unscrew it, the three pins will fall away, and the hubcap will no longer be fixed to the wheel.
Or, if it's a Hurd cap, the barrel is held in place with a screw in the side of the boss. Removal of this screw should allow you to tap the barrel inwards, or, even easier? by using a key [any Hurd key?] to rotate the entire lock/three pin assembly into the unlocked position.