I saw this watch around Europe 2 times...
First time I was buying it for parts (guys, some Cal12 parts becoming impossible to find, like 8020, 8140, 8086...): dealer knew it was assembled...
After that I found it in an important european watch market, asking price 1400 Euros.

In my opinion it's the solution of a watchmaker for change a damaged case (and we know how Monzas are delicate, black or chrome...).
Let's try to understand from wich donor!
Case is cleary not a Stowa or a Chronosport... it's 100% a Gruen, you can see it here
http://www.ebay.it/itm/Cal-12-Gruen-Heuer-Case-Crystal-Case-Back-Chronograph-/321823158490?hash=item4aee27b0da

I'm 100% sure it's not a prototype.
Jeff, it's ready for fake corner!!!!!