I was working in a house the other day and the pre-hung doors all had nickel hinges. The hinges had a bottom cap (as some hinges do) that made the top and bottom look the same. I hadn't seen this particular hinge before but didn't think anything about it. I noticed that on a couple of the hinges the bottom cap looked as if it was about to fall out (as they sometimes do) so I gave one a tap with my hammer to push it back in. It didn't slide in as I thought it would so I gave it another good whack and in it went. I went over to the other door and "fixed" it too. The next day I had to remove one of the doors to cut a hole in the jamb for a jamb switch. It turns out that the top cap is not attached to the hinge pin but instead is a threaded cap. The pin is a separate piece down inside the barrel of the hinge that you have to drive out with a punch......after you unscrew the bottom cap! Yep....the bottom cap is threaded too!
It turns out that these were some kind of special order commercial hinge. I got to replace the two hinges I "fixed". They were $30 a pair. Man was I glad I only fixed two of them!
Mike O.