"Inner Tite" barrel lock and key! With pics
The "key" is the red handled part, and it fits in the small hole on the lock. When the key is inserted and the handle folded down it pulls a spring back inside the plug and retracts two ball bearings. Here's the plug removed and the open lock:
Here's the tip of the "key" showing how the end spreads out when the handle is folded down:
Here are all the parts separately:
The key isn't the exact one for this lock, I had to file it down so it would fit the hole. If you find the actual "Inner Tite" or "Highfield" brand keys on Ebay, they are usually over $45-$50! I paid like $25 for mine, and got the lock from a utility lineman.
Here's Inner Tite's website:
http://www.inner-tite.com/
Some of their locks are quite advanced!, and they only sell to utilities and cable/phone companies, so the stuff is hard to get!
Ebay search words: "inner tite key" "highfield key" "inner tite" "barrel lock key" "meter key" "channell key"
Have fun!