From, what I can remember, the KT17's from the factory had a left and right jug. The replacement ones were interchangeable. The nonreplacement ones actually have a "1" and a "2" stamped onto them somewhere to distinguish between the left and right one. I forget where it's stamped at or even which side is which, but if you look closely at one, you'll see the numbers stamped into them.
I just looked at the manual, and the numbers are stamped into the jug under or beside the valve cover. 
This is copied out of the manual
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1980 [COLOR="Red"][/COLOR]482- Stock
1981 [COLOR="Red"][/COLOR]582- Mag18, Sleeve Hitch, Spring assist
1979 [COLOR="Red"][/COLOR]682- Mag18, Sleeve Hitch, Spring Assist, #1 Tiller
1980 [COLOR="Red"][/COLOR]782- Mag18, Sleeve Hitch
1983 [COLOR="Red"][/COLOR]982- Stock, Fully Optioned
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