Look on the bottom of the chassis for a silk-screen number ending in a -0xx with xx being a number 23 or higher. If you have one that ends in -023, then you need a specific yoke. If you have one with any other number, you need a different specific yoke. The ohm readings for each are the same, but have slightly different winding patterns. And of course the med-res version had a different yoke, too.
or if you have the original yoke, just read the number off the sticker on the side...
No original yoke to check and I am not finding any silkscreened # on the chassis.
I have one on the way. It sounds like I have a 33% chance of it working.