A discussion started over in the "Introduce Yourself" forum resulted in some photos of Park's toy rockets provided by new member "redmonds". That led to a patent number that provided this link: http://www.freepatentsonline.com/2732657.pdf
Those toys were based on that earlier patent.
Maybe now some of us can figure how those toys worked when we were too young to understand. Just keep an eye out for patent attorneys when you start building your latest invention!
Reading the description of the staging mechanism of the 2-stage rocket... a movable piston inside the booster nose provides the locking mechanism and a delay. The sustainer has a slightly flexible/squashable nozzle. The booster has an opening in the nose which the sustainer nozzle can be squeezed into but they are not locked until pressure is applied to the booster, which forces the top of a sliding piston up inside the sustainer nozzle, which spreads it and prevents it from releasing - until enough pressure is lost from the piston and booster to allow the piston to be forced down again.
The rest is about the intricacies of the one-way valves with small bleeders to let pressure out of the piston's chamber slower than it is released from the main booster chamber - that is the delay mechanism.
