To clarify, Myke Bergenske started M.R.I. It did stand for Model Rocket Industries.
MRI was bought by MPC. Myke was brought on to run the model rocket division of MPC.
MPC got out of rocketry, Myke purchased the inventory and engine making machinery.
AVI was then started selling AVI "sticker re-branded" MPC kits and supplies.
Towards the end of AVI you could get kits and engines very cheap.
Here's some more information on MRI from a phone call to Myke Bergenske himself in 2011 -
http://modelrocketbuilding.blogspot.com/search?q=mri
He led me to believe that General Mills (the parent company of MPC) got rid of MPC
rockets. In their eyes, model rockets didn't make enough money to justify their continued production.
Myke Bergenske probably doesn't get enough credit for his contributions to the hobby.
He was one of the few to build large production engine making machines.
For a short time, MPC sales exceeded Estes! MPC had great distribution already from their plastic model kit sales.
Around 1973 and 74 I built quite a few models for MPC. I got to know the Bergenske's through correspondence and at the NARAMs.