Here is a link to a dealer in Fort Worth, Texas, USA who deals in a lot of German double rifles, drillings, and verlings! www.BobJonesGuns.com

The clam shell action body was as strong as any, and was latched closed by the standard under bites, and usually with a Greener cross bolt as well. The Kerstin is simply a Greener corss bolt with two extentions fitted into resepticals one on eather side of the chambers. This type lock-up was not common on Side by side actions, but was, and still is quite common on over/under doubles from Germany, and Austria. The reason the clamshell was mostly discontinued was they found that side clips did the same thing, with far less fitting.

The BLITZ action was simply made with all the lock work mounted on a removable trigger plate, but had nothing to do with the strenth of the action, but was simply a simple way to remove the complete striker, springs, and trigger from the action for cleaning, and lubrication. This was a real advantage for field cleaning. The Blitz actions or (DETACHIBLE TRIGGER GROUP) is still being made today in many custom German, and Ferlach made double rifles.

Here is a picture of a Blitz acion trigger group!

And another view!