This one must be a fairly late one. It has the "saddle" rear sight, a cast foresight, 2 piece cocking arm and a trigger unit. The one I got was missing the spring guide, mainspring and cylinder end cap. The cocking arm was damaged at the front, which I guess was caused by brute force trying to get it out of the cylinder The pins and screws on the trigger unit had corrosion, so although I managed to get the pins out and lubricate the sear and trigger, I cannot adjust the screws
If you want to remove the foresight, you will have to take the protector off to get to the screw that holds the sight on. To remove the rearsight, knock out the split pin that secure the sight to the breech block, remove the elevation wheel and the sight will lift off. Watch out for the little spring underneath it.
Undo the 2 front stock screws and the front trigger guard screw and the action will lift out of the stock. The cocking arm will lift out of the cylinder. You can remove the pivot pin and lubricate the arm,pin and slot if you want. Knock out the barrel pivot pin. If you want to remove the barrel plunger and its spring, you need to push the plunger in and undo the little grub screw on the LHS of the block. Once you have lubricated it, replace it. (I usually use a small piece of wood to push the plunger instead of just my thumb).
Remove the cylinder end cap and the cylinder end pin and the trigger unit will come out. I would suggest getting some penetrating oil on all the trigger bits as they do seem to suffer from corrosion.
A steel ring that located the front of the trigger unit in the cylinder should also come out of the cylinder now. Using the forked bit of tube often mentioned on this thread, keep pressure on the Plug (for want of a better word) in the cylinder and undo the nut that locates it. Release pressure and the plug, guide and mainspring will come out. The piston can be removed now as well.
The piston washer is held by a forked nut. I didn't attempt to undo the nut as the piston washer was in good condition.
Clean up the bits, lubricate them and go to part 2.