Welcome Dave, you will find lots of interesting stuff on the forum. I'm over in Mt Gambier.
Now someone has to say this but your bike is not 55', its 1960 or later. Thats good though, it means you have a big journal crank and thick flange barrels, all good stuff. I have one identical, mines a 61' and black.
Dont worry too much about the seal behind the clutch, there not the best design and always seep a bit of oil.