Explain this lock to me

[El Zagna]

This door lock came from an old house I'm restoring in Calvert, Texas. The house was originally built as a county jail in 1876, but don't think this lock was part of the jail per se.

More than anything else, I would like to know what was the intent behind all the key holes, extra knobs and other mechanisms.

For example, there are two places to insert keys. The bottom one works the dead bolt as you would expect, but the other one is just another way to work the latch. Also the smaller square hole works the latch as well, but I don't see why it is needed.

My guess is that it has something to do with the missing mechanism for locking the door with the button on the face plate.

Any help you can give me is appreciated.

[Tom Gordon]

Well it is not easy to be sure from the picture but probably the hole in the faceplate is to insert a screwdriver to the follower and spindle to tighten a grub-screw.
The latch is deadlocked against "slipping" by the secondary latch It can also be deadlocked against use by the small square hole . One keyhole moves the bolt and the other one operates the "lockout" on the latch. Handles and other "operators" may be on one side of the door or both. The case is multifunction depending on the need. Similar types of mechanism are used in jails so that the "user" of one side of the door has different possibilities to those available to the "user" on the other side. This is not a high security lock though and is more likely to be a lock that was used for convenience in a guest house. Depending on what handles etc were fitted depended what function worked and the function could be changed without changing the lock. Locks are still made like this.
Cheers
Old Tom

[El Zagna]

Well, after spending a lot of time staring at this, here's what I think so far. I think the hole in the face plate is for either a lever or a button. Either way, the purpose is to freeze the doorknob. A stopworks I think it's called.

The secondary knob (the smaller square hole) and the secondary key can work the latch even when the stopwork is engaged.

I'm still stumped as to the purpose of the two small holes underneath the secondary keyhole and the one off to the side.

By the way, I believe this lock is a Norwalk.

[Dean Nickel]

I believe those two holes are key making view ports. to see if you are close to making the key right. Remember that this old of a lock would have had a key hand fit to it when it was made. You would not see these holes once this lock was installed. The second keyhole I believe was for locking down the jail at night. I have heard that it was a practice to "Bar the door" at night if there was someone of interest that someone wanted to break out of jail. This way they have to make allot of noise and give the deputy's time to mount a defense. Just my take on it.