The short extractor is not the only feature. Most Brevex actions have a 45 degree slant at the bottom front of the triggerguard - like this one that I just added to the collection. Both those with the 45 degree slant, and those with the rounded bottom front, like shown below, have all the other features that I circled.

Those are the things to look for .... including the "purple" look to the receiver, which comes from the hot blue on the high nickel content of the Brevex receivers.

I had to use photo-shop to lighten the left side to see the gas vent hole on the left front of the action - which is typical on the Brevex. The Brevex actions are the longest magnum actions made. They are about 5/16" longer than the Magnum Mauser action.

http://www.buckstix.com/buckpics/brevex-clues.jpg