Looks like that sight was held on using that two part putty type epoxy, something you can obtain at Menards or Home Depot. Plumbing Dept probably? It's like a Tootsie Roll and it actually contains both parts A & B. You just tear off a section and nead the parts togther and the putty will then set up pretty hard. I would think you could clean up the sight and reapply it if you wanted.

I actually created a taller sigh for my Trapdoor carbine so I could hunt with it. The carbine shoots very high with the sight all the way down. I just added some putty epoxy to the sight and shaped it a little. After it hardened I then filed it into a taller blade sight and filed it down until it shot to point of aim at 50 yards. Worked great. After the season I just grabbed the putty sight and wiggled it a little to break it off the original.

Now, personally, I would see if a gun smith could install a 1903 Springfield type front sight. That will look more period and a lot of sporterized Krags are set up that way.