I just refurbished the bottom bracket and where hubs on my 1985 Sequoia and thought I'd start on my 86 912. The Sequoia was pretty straight forward but the 912 is different. I'm wondering how these cranks come off. Do I use the same crank puller that I used on the Sequoia?

Those are self-extracting crank bolts. I've never used them, so I can't advise on their function, but that's what they are...

Just use an allen wrench to remove the bolt and regular crank puller tool

No. They are indeed self-extracting cranks. Use the proper size allen wrench, typically 8 mm, to loosen the center bolt. After a turn or so it will get tight again. Keep turning and the bolt will press against the outside collar (the ring with the two shallow holes on its rim). Keep turning and the crank arm will be pressed off.

You can remove the outside collar with a pin spanner and then remove the fixing bolt with an allen wrench followed by using a standard crank puller but the self-extracting bolts make this unnecessary.

Also, if that isn't the original crank a newer Octalink crank may have been installed as the Ultegra and Dura Ace (FC-6500 and FC-7700) Octalink cranks came with self-extracting bolts. If it is, a standard square taper crank puller won't work as the screw press is too small at the spindle end. You will need a specific Octalink/ISIS puller or a plug to fill the hollow spindle.

Thanks it worked like a charm

One thing to note: the original Shimano "One-Key Release" used a 6mm hex wrench to loosen/tighten. In my opinion a 6mm wrench is too small for the necessary torque. When you reinstall the cranks, you should use a standard bolt and tighten to 300 inch-pounds, remove the standard bolt and then install the One-Key Release, tightening the bolt to 300 in-lb carefully.

Back in the day when I was selling these in the shop where I worked, I saw more Shimano cranks ruined because they weren't tightened enough. Yours have survived (obviously) so you should make every effort to preserve them.