I use several LF/ULF formats, and own a long list of film holders, but today I ran across a new one on me. I recently acquired a single new-to-me 7x17 holder with no external name, and a somewhat peculiar rib lock. I previously referred to it on another post as a "no name." Well, it's not. I loaded it today, and while dusting it out, I found on the hinge the name stamped prominently in purple ink. Seebold Invisible Camera Company. With that evocative name I couldn't wait to load the film and run for Google, where I came upon an article by Rudolf Kingslake detailing the history of the Gundlach company (AKA Korona). It seems that Mr. Seebold acquired Gundlach for a short time, and changed its name to the eponymous Invisible Camera Company.
Now, if there is anything I am not when campaigning with a 7x17 and all the bells and whistles that it requires, it's invisible.
I wonder if any of you Korona shooters, or anyone else for that matter, can claim in his stable of holders a bona fide Seebold?

Yes, my Korona says that too, and I suspect the holders, which are original, probably have the same stamp. I hadn't really noticed.

Apparently this company made the first surveillance cameras, hence the name. The 7x17" camera certainly isn't "invisible." If I understand it correctly, they collaborated with a company located in the same building that manufactured movie cameras to come up with the surveillance camera.