Steve, in case you didn't know, I have seen "traditional" helical-drive machines with these control panels before, but they were Fabric-Matics. This one isn't, so I'm almost positive it's an Orbital. Looks can be deceiving, though. Only a picture of the interior will tell; I'm thinking white or blue PowerFlex agitator.
Hi John, actually, the Orbital transmission still uses the helical drive pulley, but it agitates at around 160 OPM on high speed and has a much shorter stroke than the earlier machines. It's still a touch slower than a direct-drive Kenmore's agitation (which is 180 OPM on high), however, and still spins at 618 RPM on high speed like the others. Your 11-series machine with the ivory buttons has the long-stroke transmission and agitates at 63 OPM on high speed. The AMP and early helical-drive Gyratator-equipped machines agitated at 54 OPM on high speed until they changed the transmission to 63 OPM when the Washpower automatics and Power-Fin agitator were introduced in 1966. I believe the Orbital transmission was introduced in 1988 along with the PowerFlex agitator.
Interestingly enough, the Orbital transmission can also replace a bad transmission in an older machine, provided that you install a PowerFlex agitator as well to accomodate the stroke change, as the Power-Fin *supposedly* puts stress on the transmission. However, I've been using a Power-Fin in my Orbital 'Tag going on 2 years with no problems yet.
Hope this helps.
--Austin