Since it is nearly impossible sometimes to tell that there is a pin on some T-99 front sights, I believe that after installed the pins were ground flush at each end. Which would lead me to think that the pin was put in with a lot of interference fit. I guess they never meant for them to be removed!
Find the pin head on the right side (bolt handle side) Lay the left side over a peice of steel with a 3/16" or so hole. Take a smaller than 1/8" flat face short punch and hit it hard and the pin will move and you can take a skinny punch and knock it on out. Now clamp the sight in a padded vise and twist and pull on the rifle and the sight will come right off. Reverse this to put it back on. Make a new pin by taking a 2" long peice of mild steel rod, turn it in a drill press or lather and file it till you have a slight taper and the pin will start in the hole from the left side. Drive it in the hole from the left side, cut off the excess on both sides leaving maybe 1/6" long on both sides. Now brad the excess on the right side and left. File and sand smooth, put on some cold blue and if you are very lucky it will be hard to tell it was moved. riceone.
Friend of mine sent me a very nice concentric circle rifle, it had ear on one side broken off, wanted it replaced. Sent another rifle with a good front sight but someone had cut the barrel off even with the front sight and then someone else had made a extension to make it back right only they did not put a hole in in in case someone shot it. Sent along with than another barreled receiver with a good barrel and sights to use the barrel on the one with the front end trouble. Took the good sight off the barrel with the front end trouble and put it on the concentric. Took the bad barrel out and replaced it with the barrel from the barreled receiver.
I said all that to say there are some valid reasons to tinker with sights. riceone.
Gads! If I had a broken front sight on a "keeper" it would stay broken. Guess I'll have to be sure my loupe is in my pocket at all future gunshows. Till now, I would have never suspected a mismatched sight is something I should be looking for. Yikes!