Brookfield Precision which is fabricated of steel. A good substitute would be Smith Enterprise which is a clone of the Brookfield. Once you have it mounted, don't take it off. If I'm not mistaken, the Brookfield was the one the Marines toyed with for their Designated Marksman Rifle.
I'd stay away from Springfield Inc. 2 point mount aluminum. Aluminum walks.
By the way, the U.S. Govt. Leatherwood mount is not compatible with Springfield Inc.'s 2 point aluminum mount.
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