This is a 2 pole 6 position switch. You can tell by your second photo. The two half circles near the center of the switch indicate the 2 poles. These half-circles are connected to the tabs on the left and right sides of the switch. So now that we know we have two poles, we know (by counting the number of terminals) that there are 6 different positions. 12 total terminals divided by 2 poles = 6 positions.
Do you have to have this exact model, or will a different rotary switch work in its place? By which I mean, there are similar rotary switches available which aren't necessarily made by the same manufacturer, but have the same physical structure.
If you need the exact model: Are there any part numbers on the switch?
I know radio shack has 2 pole 6 position rotary switches for about $3. Also, this link has some rotary switches:
https://www.cir.com/
They're only a couple miles from where I live, so if you need me to get you a diagram or something, I don't mind.
Also,
www.digikey.com has some rotary switches that will fit the bill, but, in my mind, they tend to over-price their switches.