Guys, I stick with auto's HDD's and industrial applications but I am also a professional pilot and this question has driven me nuts !
So I contacted a friend and professional,Darrell Morgan of FirebirdAviation.com . Darrell is a A&P and IA and a EAA tech counselor. Here's his response ;
We have been kicking around that mag switch question for a couple of days now and have come up with a consensus.
If you look at the old switches, they were labeled , Both, Left, Right, and Off, read from the 8 o'clock position counterclockwise to about the 4 o'clock position. The label/placard on the bottom. Then the switch lever would rotated from Off to Both clockwise. This is the way you would expect it to read. Right mag on the right and left on the left.
Take a look at any picture of old instrument panels.
Somewhere along the line someone decided to put the label/placard on top. Rather then re-engineer the entire switch, just label it backwards as you see them today, Off, Right, Left, Both, Start, and put the label/placard on top.
It might help to visualize this if you draw a circle, put the old on the bottom and new on top. You will see the lever action, or key, is the same.
Hope this helps,