I recently bought a very rough example of one of these and have been having a look at it. The foresight was missing and so was the wire shoulder stock and the trigger adjusting screw. The plasticware was broken and the barrel pivot pin. This will be an ongoing project and I'll have to try to find trigger springs and the other bits. HOWEVER
Remove the foresight if it has one and the cocking aid. These are secured by what appear to be 4ba grubscrews. The rearsight is on an L shaped frame and is held to the cylinder end plug by a large screw that goes in from the back of the gun. Remove the plasticware by undoing the 4 screws on each side of the pistol (My pistol has a cap under the pistol grip but when I removed it,there was no screw or hole in the frame for a screw, although some of these guns have it). Then remove the 2 screws on each side of the trigger housing that secure it to the cylinder. You do not have to touch the trigger to do the rest of the strip. The missing trigger travel adjustment screw appears to be 6ba and I managed to find one.
The cocking arm will drop out of the cylinder now. You can remove its pivot pin from the breech block if you want to lube it. Break the barrel and knock out the barrel pivot pin. The barrel and breech block will now come out. If you want to take out the plunger, you have to undo the grubscrew on the LHS of the breech block and the plunger and spring will come out for lubing. If the breech seal needs doing, you can attend to that now as well. The barrel lock up pin can be removed from the breech jaws if you want to do that as well. It is a smaller diameter than the barrel pivot one.
Push on the cylinder end plug to compress the mainspring and push the cylinder end pin out and slowly release pressure. The plug,guide,spring and piston will all come out. The piston washer on mine was in good nick and as I'm not well set up now, I did not attempt to remove it.It appears to be held on by a screw that comes from the inside of the piston and then there is a nut that would require a forked screwdriver to remove it (like some cadet majors). It appears to be a cup washer set up. Clean and lube your bits and then start to put the thing back together. Assuming you have already done the barrel plunger,breech seal and lock up pin and refitted the cocking arm, it is straight forward.
Go to part 2 STOP PRESS-- just stripped another one with a different piston set up. This appears to have a tapered pin holding a head on. The piston washer is held by a screw that would require a fork headed screwdriver to remove.