I'm Cuckoo for Thermo-Serv!

I went to the annual Gramond subdivision garage sale this past week.  It was pretty much a bust.  Participation seems to be dropping in neighborhood sales as was evidenced by this and the Canterleigh Estates sale a few weeks back.  But I didn't come away empty-handed.  I did find this Sonny the Cuckoo Cocoa Puffs Thermo-serv mug for one thin dime.

I'm pretty sure it's vintage and features Sonny in his original striped shirt.

Essentially, these mugs are simply clear plastic, watertight (usually) mugs with a paper insert.  Be warned, they sometimes leak, so take care when washing.  Considering their proliferation, there's remarkably little information about Thermo-serv on the internet.  I think most people have had a Thermo-serv mug in their homes at one time or another.  Those featuring beer labels are probably the most common.  In fact, I have a standing order from a friend to grab any beer-themed Thermo-serv mugs I come across.  Even the Farrah cup I found a few weeks back was a Thermo-serv.  Searching the internet, I found no other examples of the Cocoa Puffs mug or any other cereal-themed Thermo-serv mugs.  Anyone seen one of these before?