Some thoughts about taking your lock apart.
First, let me say it is best to have a mainspring vise like they sell at TOTW or Dixie.
These have a long 'foot' on them that rests against the lower part of the spring. It spreads the load out making it much less likely that the spring will break.
Lacking one of those, if you want to take the risk, you might want to try using some Vise Grips.
I've looked at your lock photos and it looks like there is a lot of length aft of the upper end where the Vise Grips would have to grab.
That makes me suggest that using a piece of 1/8" thick steel under the lower leaf to spread the load might be a good idea.
Anyway, the vise or Vise Grips are not used to actually compress the spring. It is used to hold it in a compressed position.
To do this, cock the hammer to full cock. This will straighten out the lower leaf.
Put the support or mainspring vise on the spring so it is resting under the deflected lower leaf.
Using the thumb screw or knurled knob, close the jaws of the vise or Vise Grips so it is grasping the upper leaf and firmly restraining the lower leaf.
Now, release the sear to allow the hammer to fall.
If your lucky, the hammer will rotate far enough to completely release the tension on the now restrained mainspring.
Once this happens, gently rock the vise/Vise Grips and spring and its tab should pull out of the lockplate. Lay the spring & vise/Vise Grips aside.
With the mainspring removed, now remove the sear spring and its tab from the lockplate.
Now, remove the sear.
After removing the screw that holds the hammer onto the tumbler, get two pieces of wood that are at least 1/2" thick.
Place the blocks of wood, one on either side of the tumbler and sit it on a stout table or counter with the tumbler on the underside of the lockplate.
Get a drift or something made of steel, brass or copper that can fit down thru the square hole in the hammer and rest against the square drive on the tumbler.
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Place it against the square end of the tumbler and use a small hammer/mallet to drive the tumblers square out of the hammer.
The tumbler will fall to the table.
You could also use a bench vise with the jaws opened up so the tumbler can fit down between them to support the lockplate. Do not clamp the jaws.
The only catch with the vise is when the tumbler is driven out of the hammer, it will fall to the floor and rapidly run under the biggest pile of manure on the floor that it can find.
It is very fast and can do this before you can see where it went.
Congratulations! Your lock is disassembled.
The only comments about reassembling the lock is you need to be careful about the position of the hammer before you tap it back in place on the tumbler. Also, it's usually a bad idea to try to use the hammer screw to force the hammer back on the tumbler square.
Have fun.
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