Yes, there is an outdoor switch on the pole. If that livestock area isn't being used, the lamp is powered down. (Most of the time it stays on.) The sink bowl is actually a very effective cutoff reflector. It throws a good pattern with almost no "stray" light. Some of this old stuff is still very practical.
Ah I see. Yeah these reflectors are very cool. Never seen anything like these. Like a cross between a crescent moon and a radial wave. Was there a purpose for the extra rim on the sides of the reflector? Just to make the reflector a perfect circle or did it serve an actual purpose?
Steve may have a more accurate answer but I think the round rim is more for aesthetics. I have to admit that when the lamp is positioned correctly in the fixture, this design produces a really effective light pattern and at the same time, especially for such an old design, has really good cutoff characteristics. I'm posting to the gallery a night shot that I just took.