$250 is fair depending on condition and what else it has on it.
Level 10?
Single or Double trigger?
Included Barrel/kind?
Overall condition?
Nice anno?
I would say $250 is about the most you should pay for a classic valved mag.You could always go RT ULE custom brand new for $340 so.....
hAir trigger info here.......
http://www.automags.org/forums/showthread.php?t=130476