I bought a classic mag from my buddy the other day, it worked just fine except that the shoot down was really bad. I plan on giving this marker to my 12 year old nephew for his birthday so my plan was to take it apart put all new orings in it and clean it up nice. I pulled the on/off out and found this.

Anybody know if its AGD or some aftermarket on/off, it doesn't match any of the pics I can find on the internet so I don't know how to put it back in.