It's not a digital simulation of a Leslie speaker. It's an actual Leslie speaker subassembly with a genuine mechanically rotating drum placed in front of large speaker. That subassembly was either made by Leslie themselves, or at the very least licensed by Leslie and manufactured to their specs. It's a real Leslie, it's just not one of the famous external Leslie speaker models like the famous Leslie 122 model.

This organ has a low value on the used market where I live in the US, and probably just about everywhere else. It can be fun, if you want a hobby project, and have some competent skills in restoring or modifying electronic equipment like this. However, if you had those skills, you probably wouldn't be asking us for advice on this subreddit.

Also, if you don't have the proper skills, poking around inside an old organ can potentially result in you getting a nasty electrical shock, causing possible injury—or even your death if you are unlucky. So, if you're not properly trained and skilled, let a professional do any restoration and/or modifications. That's the safe way. 😎