Can you help me identify the manufacturer?

Thanks for posting. In most cases, the manufacturer is irrelevant to identifying the right replacement handle set since most manufacturers use generic hardware. There are some niche exceptions certainly, but in most cases the hole spacing is what matters most. Either way, there's a good chance your handle set is used by a million different manufacturers.

Usually I like asking for photos of the original handle set, as well as the mortise lock, just to account for other possible factors like the positioning of the thumb lever (is it center or offset?) or if this is a special-case handle set. If you could show us those photos, as well as confirm the hole spacing, we should be able to identify possible replacements for you.

Thank you, these pictures are indeed a huge help. This is a generic handle set, so knowing the manufacturer wouldn't have been a big help after all, like Bob said. Specifically, you have the 82-035 along with what looks like an 82-315 key lock on the outside handle. You may want to consider going with our 82-086, which comes with a key lock and should work in the same capacity.

You also mention that the handle won't lay flush with the door. That may be because the screw bosses are too big for the holes in your door. This is a common issue. An easy fix would be to take a rat tail file and make the holes bigger by just a hair. It'll be a trial and error sort of thing; you'll have to file it a bit, try the handle, and then file again if they're still too small. Let me know what you think!

Awesome, thank you! Please let us know how it works out or if you run into any issues, I'd be happy to help.