Looking at the pictures in the link Wavedancer provided, do you have the Sunfish-like S-Cat or the dinghy style Surprise?
The Lockley-Newport company that made these boats went out of business almost 20 years ago. Original parts and manuals are scarce, but being similar to other designs, adaptable parts and the rigging can be worked out.
Double-check that serial number... I think it's probably NPT0615SM786. In which case, what you have is a Lockley-Newport Surprise. Does it have an exclamation mark on the mainsail?
I have the 1977 model.
I've attached the manual and the original manufacturer's brochure.
If you have any specific questions, let me know. The manual could really use some illustrations. If you need to see how something is rigged, I'll be glad to take pictures of my boat and send them to you.