How to check for check valves.

I recently purchased a 4way distributor for my kegerator off of ebay. The valves look identical to the ones on this setup http://stores.kegconnection.com/Detail.bok?no=53. How can I tell if they have check valves or not? I can blow air through the input barb and air comes out the valves that would be going to the kegs. I can blow air back through the valves that would be going to the kegs and it comes out the input. I can also hold my finger over the input and blow air into one of the keg valves and it comes out the other keg valves. I have not tried using it with co2 yet. What am I missing, or did I just get the screw?

It sounds to me like there are no check valves.

ew… :-\