In the case of the silver miliarensia, first issued by Constantine the Great, the types are either identical, or closely connected, with those of their comparatively rare silver multiples, or money medallions, where such corresponding multiples exist; and while there are many miliarensia for which no corresponding multiples are known and a certain number of multiples for which we have no corresponding miliarensia, such combinations as we do possess definitely suggest that the miliarensia formed part of the same series as the multiples and were issued for the same occasions.
Source: wiktionary
The discovery of the above obv. coupled with the rev. type of ‘four standards’ and a comparison with the obv. of no. 99 necessitates a few comments with regard to the date of these two miliarensia, both marked CONS (only the v. Echt specimen of no. 99 has been available for comparison).
Source: wiktionary
The silver miliarensia from that era were minted exclusively for propaganda purposes, and in smaller amounts than the gold coins (nomismas) and the copper alloy coins (folles). They were practically not used in circulation, although in theory twelve miliarensia were equal in value to a gold nomisma.
Source: wiktionary