This handle assembly is missing the flat, sliding plate that engages the keeper. I can't find any info on the door or frame, but I think it's a 1970s or 1980s vintage. I hope this is enough to identify it.
Bob from SWISCO responded:
October 4, 2019
Thanks for writing in. This handle set looks like it could be either the 82-036 or 82-078, depending on the style of the hook. I am afraid we don't carry the internal mortise lock, and I am not sure if it's available any longer. I apologize for any inconvenience.