Hi Mike
Not sure which you are looking for the Key type with armored cable or thumb switch with the armored cable. My experience with the 12 is that they are the same switch one having a key with thump lever attached to a key stub or just a thumb lever with a barb that pushes into the switch and the switch doesn't really have a tumblers.
Here is a short video of taking the lock apart
https://www.youtube.com/watch?v=yi3P03DxP_s
If you have a key type with tumblers and a key that fits and one of the thumb levers you can look at just cutting off the key inserting it in the lock and then putting the thumb lever in place. Problem I've had with the thumb levers is the barb that holds it in place often breaks off. I've use a little epoxy glue to hold it in place.
Cheers Phil