Remove S-Type Keg Spear - Easy, non-destructive method using keg coupler

How to remove an S-Type (Euro-Sanke/Sankey) spear from a brewery keg. This is a simple method using the appropriate D/S-type coupler and a coin. Several suggestions of this method appear in forums. It's a helluva lot safer and less destructive than going at it with hammers and screwdrivers.

Skip to 3:30 to skip the commentary and just show me...

TLDW:
The spear assembly is removed by rotating it counter-clockwise. The two small locking tabs visible on the top of the spear/valve assembly serve two functions: to allow the keg coupler to be locked in place, and to provide a lever point to insert/remove the spear at the brewery. But we need a special tool to do that? No...
1 - Place the coupler the coupler into the valve as per normal, but don't rotate CW to lock it, instead rotate it CCW and notice that the tabs on the coupler butt up against the tabs on the valve. Use the coupler as your valve removal wrench.*

2- After a while of unscrewing, you will find safety locking flanges (to stop the spear flying out under pressure if someone was dumb enough to unscrew it while filled) stop you fully removing the spear.

The spear has to be pushed down to release the safety locking mechanism, and further than it would be by the coupler's probe when engaging it to unseal it and extract liquid. We can just put a coin on top of the spear to depress it further.

Remove the coupler, and place a small coin on top of the spear. I find an Australian 10 or 20 cent coin works fine. It needs to be thick enough to sufficiently depress the spear, but no larger diameter than the sealing washer around the spear, so that it isn't prevented from moving when pushed by the probe.

Insert the coupler as per normal, locking it into place and releasing the safety mechanism. As the valve assembly has already been unscrewed most of the way, friction alone between the coupler and valve should be sufficient to allow you to unscrew the assembly all the way out.

3- Reinsertion. Just step 2 in reverse. You need to depress the safety tabs using the coupler+coin, then rotate CW until it's sealed up.

*There are a few comments below saying this doesn't work. I suspect the problem is applying sufficient torque to unscrew the valve, initially to loosen it. The coupler doesn't give you a huge lever arm action, and applying enough torque if the threads are seized, or it's in real tight might not be possible. This is now an exercise in removing a stubborn bolt with an annoying spline drive interface. In that case I'd try to fashion some sort of extension lever to apply more force with the coupler, find someone stronger, soak it in WD40 (and then give it a real good clean), make a custom socket tool to attach it to an impact wrench etc. Consider putting some PTFE tape on the threads when re-sealing if it's a recurrent problem.