The Collection: Emhart Interlocking
Channel: Schuyler Towne
Date: 2014-08-28

Great little lock, I recommend you check out the patent: https://www.google.com/patents/US4103526

And while you can't go out and buy one today, Corbin/Russwin kept making new ones for quite a while. Here's one of their catalogs that has some additional details: 
http://lock.gd/corbin-emhart.pdf

If any of you EVER happen upon an Interchangable Core (IC) Emhart lock, hit me up! I'd love to see it.

(Also - I bumped up the gain on this, and all subsequent collections videos by 10db. Those of you who have been following the audio issues, let me know in the comments if that's working out for you)