This folder "locking feature" you describe is called Folder Protection. It gives you the ability to protect the System Folder or Applications folder from change or accidental deletion. It is a function of System 7.5, not of the hardware. In other words, this function will work on any Macintosh computer running System 7.5 if the system software is set up correctly and operating properly.
Most likely, what is "wrong" on some of your Macintosh computers is that File Sharing is turned on. Folder Protection will not work if File Sharing is on. When File Sharing is on, the Folder Protection options in the General Controls control panel are unavailable, and therefore are dimmed.
Check the Sharing Setup control panel to see whether File Sharing is on or off. If it is on, you will have to turn it off if you want to enable the Folder Protection feature. File Sharing and Folder Protection cannot be on at the same time; you can use one or the other. File Sharing automatically turns off the Folder Protection feature when it is turned on.
Copying the General Controls control panel to lock all of your computers' System Folders will not work because the system settings will be reset as soon as File Sharing is turned on.
System 7.5.3
With System 7.5.3, if folder protection is turned on for both the System Folder and Applications folder, these folders cannot be renamed because of the protection feature. If File Sharing is subsequently turned on, the folder protection options in the General Controls control panel are dimmed. However, the System Folder and Applications folder cannot be renamed as if folder protection had not been turned off.
By opening and closing the General Controls control panel you can then rename the protected folders.
Turning on File Sharing does not actually turn off folder protection if it had been previously turned on. Because File Sharing is turned on, however, opening and closing the General Controls control panel turns it off because the buttons are disabled.