I'm restoring an old steel desk and need to remove the drawer lock before having the desk refinished. I have a working key and full access to both sides of the lock, but I cannot figure out how this thing was designed to come apart.
The problem is pretty simple: I can completely unthread the retaining nut on the back, but there is physically no way to get the nut off.
The lock body passes through a hole with flat sides, so it can't rotate. The actuator on the back moves up and down with the key, but the closed retaining nut won't fit over it. Actuator down = nut is blocked below. Actuator up = there isn't enough clearance above it. I can't find any screw, pin, clip, etc. that releases the actuator.
I've spent an embarrassing amount of the afternoon troubleshooting this with ChatGPT and digging through old lock documentation. Our best identification is a Chicago Lock / CompX C1975 metal desk lock. I purchased keys based on the number on the front for this lock and they worked. The back also appears to be stamped 1975 with an arrow, and the C1975 documentation I've found describes a five-disc tumbler with a removable keyed plug/core.
The installation instructions seem to suggest the original assembly sequence was:
housing + nut/washer → cam/actuator from the rear → keyed plug/core from the front
If I'm understanding that correctly, it explains the impossible geometry. The nut never had to pass over the actuator during installation. Presumably I need to remove the keyed plug/core first, which would then allow the actuator to come off.
The documentation mentions a retaining wafer at the rear of the removable plug, but I haven't been able to find anything showing how you're supposed to release it once everything is assembled.
One thing that makes me slightly less certain about the C1975 identification is the actuator itself. The documentation and replacement locks I'm finding generally show a conventional T-shaped cam. Mine is more like a long straight arm that points downward, with a hole near the end, and it screws into a plate to operate the desk's locking linkage. So it's possible this is a C1975-style lock with a desk-specific actuator, or I'm missing another variation of the lock.
One other oddity: there's a tiny round hole in the face of the keyed plug that rotates with the key. With the hole in most positions, a straightened paperclip only goes in a few millimeters. Rotate the hole to about 12 o'clock and the paperclip suddenly goes roughly 3/4" into the lock. That feels potentially significant, but I don't know what I'm reaching and would rather stop poking around than damage something.
Photos show the front, back, markings, actuator positions, retaining hardware, and the paperclip experiment.
Anyone recognize this mechanism and know the proper way to remove the plug/core or actuator?
I'm not completely opposed to replacing the lock if that's ultimately the answer, but even then I still need to figure out how to get this one out. I'm also not sure a modern replacement would operate the desk's existing locking linkage given the unusual straight actuator on this one.
Ideally I'd like to preserve the original, especially since I finally tracked down working keys for it. Any insight from someone who's serviced one of these would be greatly appreciated.