Ever seen something as weird as this?. Rated at 15W at 230V, the thing is, it has 3 pins, not two as your standard Bayonet cap bulb. BTW here is the pic:
Sorry the other 2 pins are out of the frame, but this is not the first time I have seen lamps with this configuration. Why would you have 3 pins on a lightbulb?. Your guess is as good as mine so, go ahead!.
May be a silly response, but assuming that the other two pins look like the one shown, could they be for the purpose of keeping the bulb seated in the socket - a sort of bayonet device (push the bulb in and rotate it a short distance to the right or left?
Wild decorating on the outside, too...
The three way lamps we have in the USA start off with the same type of medium base screw shell, with the difference being the construction of the "button" in the insulating middle of the shell - a small button in the center, and a somewhat larger "ring" that encircles the space between the button and the shell. Shell is common to both filaments, with button as hot for one filament and the ring as hot for the other filament.
[This message has been edited by mamills (edited 12-01-2006).]
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.
As for the "wacky" paint job, I've seen very similar paint jobs on bulbs here in the USA. You can usually find them at Wal-Mart and places like that, usually 25 watt bulbs with wild paint decorations. They are sold as novelty "party" bulbs, just meant to be displayed in open fixtures, strictly for their decorative appeal.
I actually saw a bulb very close to this the other day. It was an orange color with the same type of size and base. When I asked what it was out of the customer replied that it was out of an electric fireplace that came from Europe. Also he said that the bulb made a flickering type of light.
Groovy color scheme..... If you weren't "down under" I'd think it came right out of the Haight-Ashbury district!
In line with Allen's comment, I've seen porcelain/brass BC lampholders in old electric heaters which have the three locating pins instead of the usual two. I don't recall ever seeing any bulbs in them though -- Possibly because they are no longer available?
Why a domestic electric heating appliance ever needed such an oddball configuration is anybody's guess. Plenty of other heaters had the regular BC lampholders and "Fireglow" or similar flickering amber/red bulbs for those are still obtainable.