From what I can find on ismacs it's a model 28K, the K indicates it was made in Kilbowie Scotland. I wonder how it found its' way to Cedar Hill USA? The chromed plates should shine up very well with a bit of metal polish. Be careful when cleaning the decals, only ever so gently, but it should shine up nicely. Does it stitch?
Here's a pdf manual. It's fairly straight forward to use it. It might be a bit unusual threading the shuttle, and tension release on the upper thread is not connected to the presser bar lever, but is the tiny press in part on the tensioner.