ldl window, sliding door handle and lock mechanism, from 2004

Thanks for posting! Your patio door mortise lock reminds me of the 82-080 Mortise Style Handle Set, the keyed version of this set is the 82-081. To confirm that this is the correct replacement, carefully review and compare the dimensions below.

Dimensions for 82-080

Your mortise lock appears to be missing it's faceplate but the body resembles the one used for the 82-238 Double Hook Mortise Lock. Take a look over the dimensions to determine if this is the right fit for your door.

Alternate image for 82-238

Alternate view of 82-238