The serial no is NS1
It has a mark 1 villiers ignition
The motor is very original except the tank being blue.
Have done some repairs
broken tiller handle rewelded
a couple of broken bolts replaced
A replacement piston and new rings, the original was in very poor condition as the motor had been seized for years before i bought it,
the replacement piston came out of a 1945 sd model.
I have also replaced the original carbie as it was in very poor condition and I couldn't get it to run reliable.
The motor still does a lot of work, I use it as my main motor as I prefer it to my later model silver century.
also have a 1955 102 and a century 100 which is in excellent condition plus lots of bits and pieces