If you are like me, the most glaring defect in a rep Panerai is the crown guard. It doesn't move smoothly, some lock closed too much, some not at all and the pin... After receiving my PAM 111H from Andrew, day 1 the crown guard fell off. Don't ask how I found the pieces, but I did.
Step 1 was to open the back and gently back out the winding stem about 1/2mm before tightening the screw. This gave just enough room for the crown guard to lock in with a positive snap but not so much that it wouldn't open easily.
Step 2 was to remove the entire crown guard assembly. You could remove the pin from the back using a bracelet tool, in my case the pin was already out. I inserted the pin through the guard and lever and used a small amount of crazy glue on the underside of the crown guard. The glue allowed me to hold the pin in place and leave the top of it a little high.
My rep, and just about all of them I have seen had the pin driven in place leaving a mark on the top, as well as being recessed. I have seen authentic Panerai's with recessed pins, but I think it looks much more professional to have a flush pin. And definitely no mark on the top.
With the pin slightly proud, I then placed a sheet of 600 grit wet dry sandpaper flat on a table, and carefully sanded the top of the crown guard moving the guard and not the paper. It surprisingly only took a couple of minutes for a nice flush finish. The result: