[saxman]

Yes, the side plate should match the rest of the finish on the side - it would stick out like a sore thumb otherwise. I don't think he's going to burn up any 'stahl' with a propane torch, but it is possible to take the temper out of springs at propane temperatures. I think one secret to fire blue is the polishing before heating. It must be fairly easy to do, because there are a lot of fire-blued springs around for different purposes. I saw some Colt revolvers at a show - gold-plated with fire-blued screws - very beautiful.
Ken; on the trigger plate, you might try wet/dry paper on sanding blocks to maintain the flat surfaces, and roll the paper on a drill bit or similar object for the radiused sides around the lever housing. Very difficult to keep the factory look to a plate that has to be de-pitted, and a rounded, 'soft' plate really looks bad. I have a trigger plate that someone down the line tried to de-pit with a drill press (I think) with some kind of burr in it. It looked so bad that I put a mismatched plate on the gun with original finish that luckily matched my Luger. It's an Erfurt on a DWM, but it's just a shooter. If it wasn't for the Erfurt inspector's stamp and the wrong number, you'd think it was the original. Snapped in with no fitting at all. Good luck on your project, and keep us informed.