What's the difference between an open and closed cam shoe?

Thanks for writing in. This is a very good question. It actually does make a difference. The 15-195's cam has a 'wall' in the back, whereas the 15-195B cam you can see 'through', hence Open Cam. The style of this cam affects what pivot bar is compatible with the shoe, so it certainly is best to choose the correct one. 

The 15-195 comes installed by default with our Series 795 Channel Balances; if you need the 15-195B or a different shoe, you can buy it separately and swap the shoes. See the video below. 

Hello, Nan. Your cam is technically closed, but that's not really relevant to your project. They don't make an open cam version of your shoe. It should also be noted that your hardware is very, very different from the video above. Your balance system has a very different configuration and isn't compatible with the hardware mentioned above in any way.

I'd be happy to look into it for you, but I would need to see photos of your old balance to have a better idea of what you have.