Well it could be a forgery.

However the dotted R and the hooked X were not generally known in the 19th century. Also the 'Easter count' used by Cistercian monks to authenticate the date would seem to contribute to authenticy. Either Olf Ohman had extensive knowledge of obscure medieval runes to create the forgery or the engraving is authentic.

"The Stone Age did not end for lack of stone, and the Oil Age will end long before the world runs out of oil"

-- Sheikh Zaki Yamani