panther463 welcome to the best Silverwing forum on the net. This link will show different number locations. Useful Silverwing number locations
If you've gotten rid of the cowling you should have it on your title. Just curious, what do you want the number for? If it's for your DMV you need to check with them to find out how to replace it.
It would be nice if you went Here and introduced yourself.
Then you'd get a proper welcome from the forum members.
If you are looking forward to learning and plan on doing your own maintenance you'll find you can do anything you need or want with the service manual and help from this forum.
I add the paragraph below for most new members because there's a lot of information in the links and may save you some work.
Here are some links(3 below in blue)that will help you learn a lot about your Silverwing. If you can't find what you need in the links below the search on this forum works good, and if you still need help just ask and someone will do what they can to answer your questions. Maintenance, Tips and HintsMaintenance "Pictorials" Accessories-Modifications