I had an opportunity to look at the A-1215, and the later 6 series CJ2A caps this week. I don't remember any mention of a chain.
I will add that a brand new cap from a reputable supplier was a high pressure cap and caused head gasket leakage.
The spec calls for the valve to open at 3.5 to 4.5 PSI of pressure, or 1 psi of siphon.
The new cap was stamped 4 psi, but was more like 15-20 pounds. I didn't have my cap tester with me, and I doubt I had an adapter for a cap that big anyway...
MVPA # 419