The pins on the sides of the cap are just to latch the bulb in the socket.

Electricity goes to the filament via two contacts (solder blobs, essentially) at the bottom. Similar to the center contact in a screw-base lamp.

The third peg on the cap was probably a way to thief-proof the bulb -- nobody would bother stealing it if they couldn't latch it into their socket at home. The theory would be similar to left-handed screw-in bulbs.

I can't explain the wacky paint job, though. [Linked Image]