"at one time a lot of bad Brevex actions floating around and also some fake Brevexes around"

Care to elaborate? I've owned more than a few in 45 years of gun collecting, never heard of such a thing.

Here's some specs from Bolt Action Rifles by Frank de Haas

The number in brackets are the specs of a M98 large ring.

Weight - 53 oz(45 oz)
Length - 9.25"(8.75")
Receiver Ring Dia - 1.50"(1.41")
Bolt Dia - .700"(.700")
Bolt Travel - 4.975"(4.57")
Striker Travel - .550"(.535")
Magazine length - 3.925"
Magazine Well Width - .665"
Guard Screw Spacing - 8.25"(7.825")
Barrel Shank and Thread Dia - 29 X 2 mm(approx 1.141 X 12.7 V treads/inch)

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I think that the biggest difference is that the Brevex was made with the ways pulled all the way through on both sides.
This made the action less labor intensive to produce but also did away with the mauser 'inner ring' or C ring. In regular use a minor difference. In the event of case failure not everything is vented away from the shooter. Those hot gases and bits of molten case can ruin your whole day!!!