Ken,

I am not familiar with the type of valve you show in the pictures. I have not seen that type of valve with three nipples before. I have successfully used a similar valve from BVM. Find it here at the bottom of the page:

http://bvmjets.com/Pages/Catalog/air.htm

It looks like yours might be a BVM unit but I am at a loss to explain that 3rd air nipple. You can see that the BVM unit has a hole where your third nipple is.