if it's National, I posted quite a few manuals on VSS where you can download them for free. You just have to look at the pictures and match up your machine.
The one in the link above that is NOT a 15 clone, I know I have the manual posted for that. I think that is the Expert BT - not sure though. I have a couple like that one.
These three are all National made "godzilla" finish machines. With Nationals, the name on the machine isn't usually helpful.