The lock is for a sliding door.

This looks like our 82-226 Mortise Lock, however your setup is a little unusual. It looks like the key lock on the outside pull and the thumb latch on the inside are not aligned, when they really should be for the door to work properly. Just to be safe, please remove the mortise lock from the door so we can have a better look. Many thanks. 

The 82-226 is the best possible assessment I can give without further data. Again, the positioning of the key lock and thumb lever seems very odd to me, so that's just something to keep in mind. But this is my best answer without further details. Let me know if you have further questions.