The existence of a general exchange medium in Moravia has not been proven: there is no sign of local coinage and foreign coins are scarce. According to Bialeková and other archaeologists, the axe-shaped ingots (grivnas) unearthed in great number in fortresses served as "premonetary currencies". This theory has not universally been accepted, because these objects have also been interpreted as "intermediate products intended for further treatment". According to Macháček, the lack of coins meant that Moravian monarchs could not "effectively collect taxes, customs and fines", which weakened their international position.