The remains of the original sticker would indicate that it's an original, never messed with booster.
It's always a good idea to have your booster rebuilt. Most of the time they will give you some warning when they are starting to fail, but every so often they don't. I had one fail on me with no warning what soever, and it can be a really bad situation when your stopping distance unexpectedly doubles on you. Thankfully, I was on a quiet back road when mine failed. If I had been coming up on stopped traffic, it could have been a disaster.
Jeff