Mont. Code Ann. § 81-4-219

For the purposes of 81-4-218 through 81-4-220, it shall be prima facie evidence that such boundaries are properly marked if the same are defined; provided that such monuments or some tree, stump, or post adjacent thereto shall be conspicuously marked with the name of the owner or claimant of such ground and the name of the claim or the description of the land claimed.