Does this lock exist?

[jonwil]

Does a deadbolt exist where it has 2 different keys. If the deadbolt is locked by key A, it can be unlocked by key A or key B but if it is locked by key B, it can only be unlocked by key B and not key A?

[billdeserthills]

It isn't hard to make a pin tumbler Lock work the way you describe, over the years I have modified a few of my clients locks to work as you've described.
Generally this was done so a maid could Lock the deadbolt upon leaving, yet not have the ability to unlock that deadbolt

[Squelchtone]

Here's a post from 2006 about this, but the images are no longer hosted so you have to use your imagination

https://www.lockpicking101.com/viewtopic.php?f=9&t=15918

[Safecrackin Sammy]

Hotel function mortise lock may fit your need.

[Raymond]

I sent jonwil a PM requesting a direct email address on the 7th so I can send a Word file with a working solution. I have had no reply.

[GWiens2001]

Hotel lockout keys with their second bible could do it.

Gordon