Originally Posted by Teamfoxy
I cannot directly answer the OP's question because I do not know how the coach is wired. But I do know that there are 24volt electrical systems out there and the answer below may be incorrect.
Here is the link to an an article on the subject of 24Volt systems in RV's:
Why You Should Convert Your RV to 24 Volts DC
Most starters are 12V, so require that voltage. But 24V alternators are available to charge all the banks of a 24V system at once. So in some 24V systems, there is a provision to temporarily put two 12V batteries in parallel in order to start the engine. After the engine starts, the batteries are switched back to be in series. There is usually some method of keeping the alternator off line until the engine is running and the batteries are placed in series again.
I'd suggest the OP check with Winnebago (or the previous owner) and find out if this is a factory installation or something installed later. Hopefully they could answer the question.
Chris's answer is DEAD ON! About 99.9999% of the factory coaches produced are 12V. There might be a really, really rare case where a coaches system is 24V but, not normally in the American market, especially in the era we're speaking of. I too am wondering what the OP's meaning of a "Jumper" is. Unless the coach's batteries, either chassis or house, have been tampered with and or all the wires and cables removed, not sure what a "Jumper" would be for.
Also, as Chris has stated, there is a form of a built in "Jump" system. It's the Auxiliary Batter Boost switch which, when depressed, engages a rather large solenoid, way back in the shore power compartment, in a hidden compartment, that couples the house batteries with the chassis batteries for augmented engine cranking. If the OP ever returns, we "might" see what he was looking for.