Joker Poker was manufactured as an EM as well as a SS.
I have both a SS JP and a Count-Down and love them both.
CD is so simple, rules wise, yet so addictive. 16 drop targets.
JP 15 drops.
I have repaired dozens of Gottlieb System 1's. The MPU/CPU PCB is a piece of shit but can be repaired. They suffer from corroision and battery acid on the fingers, tracks and components.
The harness contacts, many, many need to be replaced.
The Driver PCB is easily repairable. The Power Supply is also repairable but is a pain to dis- reassemble due to the 5VDC pass transistor.
See this thread for my way of dealing with repairing the 5 VDC pass transistor.
http://pinside.com/pinball/forum/topic/gottlieb-system-1-power-supply-mod#post-235628
Rottendog sells replacement PS, Others sell replacement Driver PCBs.
The king however is the Pascal Janin MPU/CPU PCB or His all-in-one PCB.
Once you have the Pins all fixed mechanically, harness etc, the Pascal PCBs make the Gottlieb System 1s Rock Solid.
Of Course get the Clay System 1 guide for all you need to know about these Pins.
If the price is right I would grab them. Do you know what the guy is asking for them?