Mercer window lock
Thanks for writing in. Try popping off that name plate. I believe you'll find the installation screws there, so you can then remove and replace the lock. If you're also seeking the right replacement, take a look at the 90-323 and let me know if that's what you need.
Awesome! Let me know if you need anything else. Thanks for considering our business, we appreciate it.
It sounds like your lock broke off while it was stuck in the locked position. I'm afraid there's no real trick to that. If you aren't able to rig it open then it might need to be cut off.
I would recommend contacting a local professional to come out and get a pair of hands on it. This may be a hassle to remove.