I wish I could remember where I read it, but supposedly one of these were liberated from the guards at Dachua by a vet.
Here's a discussion from 2005 on another forum which suggested that these may have been reworked by Klett. Back then I actually sent a letter to Klett Gunsmiths in Germany looking for a family connection or info but never received a response back. If I'm in violation by posting the link, please delete and let me know.