The Mongoose is basically a blowback marker with an E-frame on it. They were around in the early 2000's and faded out. They're the same design as the Spyder, Icon, Piranha, etc. Did you ask the guy at the shop to air it up and show you that it fires properly?
Even if you get the marker for $35, you're still going to need a tank, hopper and mask to play. Does it come with any of those?
If you go to the B/S/T section on this website you can find people selling gun packages and used equipment (newer than the Mongoose) for close to the same price.
Fully upped Ninja 2k2 STO w/ Check-It Pump Kit
Play Pump. ಠ_ಠ
"Originally posted by BallSoHard2012: So YOU were the guys that stole those captures at the end of the main-game!? -Mack (MCM MVP)"