regarding sparky's tandem/parallel outlet:
At one time, there were two styles of 110-volt/two-pin plugs. One was the regular parallel blade plug and another called "tandem." The outlet was designed so you could use either type.
Later outlets would use T-shaped holes for the same purpose.
Look at the following pictures in this website and you'll see pictures of the outlets and the tandem plug that would have fit it:
http://home.netcom.com/~wa2ise/power/power.htm
--
sven
