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Regarding the compass, don't forget, if you want to go 100% accurate, you can always go with a Silva Type 12 compass and the outside nylon sheath pouch, which Buck went to after continuous problems with the button compass in the buttcap. It will probably be next to impossible to find the original button compass, but the Silva compass and the nylon pouch occasionally pops up on eBay. Does your Buckmaster have a compass in the buttcap that needs replacing or did you just want to add one? If it doesn't have a compass, then your knife came with the Silva compass originally.