Marks of value and an episemon

[Victor]

There are very few issues of Roman coins with marks of value on them, however there is one series that is fairly common.

In the right field of the coin pictured below (RIC VII Nicomedia 43) there is an  X over II and an episemon - "The last sign is clearly an episemon, epigraphically employed for S(emis) also."   (RIC VII p. 12)           Semis literally means half, and the semis coin was valued at half an as.

The IOVI coins were issued as part of a coin reform by Licinius in his territories (mints of Heraclea, Nicomedia, Cyzicus, Antioch, and Alexandria) and were reduced in value from 25 to 12 and a half.  The coins were worth less because they had little or no silver. He struck these in the names of all the rulers but these coins had no value outside his territory.  As a result, these coins are sometimes found overstruck with other types--note the second picture below for an example.

[Genio popvli romani]

Just a graph to illustrate your words about the rate of silver in the Eastern coins issued by  Licinius (~2% Ag in Western mints / ~0,2% Ag in Eastern mints).



In deed, a valuable operation made by counterfeiters, no fastidious work with flans, just the stamping process and the coin was worth twice.

[Victor]

From Analyse de monnaies de bronze (318-340) par activation neutronique à l'aide d'une source isotopique de Californium 252 / Jean-Noël Barrandon, Claude Brenot

Here is a link to the article-

http://www.constantinethegreatcoins.com/articles/Barrandon_analysis.pdf

[Nikko]

"Dionysius to Apion, greeting. The divine Fortune of our masters has ordained that the Italian coinage be reduced to the half of a nummus. Make haste, therefore, to spend all the Italian silver that you have in purchases, on my behalf, of goods of every description at whatever prices you find them. For this purpose I have dispatched an officialis to you. But take notice that should you intend to indulge in any malpractices I shall not allows you to do so. I pray, my brother, that you may long be in health. (Verso) I received the letter from the officials on the eight of the month Pharmouthi."
Letter in Archive of official Theophanes, c. 321 (P. Rylands IV. 607)

Actually we stil ignore why Licinius did this monetary reform but at that times it probably caused a great stir.
By the way, it should have been a complete failure: it didn't help  the monetary system to return in balance. Half-nummi are absent in eastern hoards so, according to Gresham's Law, they must have been "bad" coins.
These coins were not accepted and could not circulate through Constantine's territories and after Licinius defeat, half-nummi were demonetized (Harl, Coinage in the Roman Economy, pp. 158-166).

[Genio popvli romani]

The first one looks like a pretty official coin. I guess these coins were not silvered anymore after they had been struck twice, and their odd origin should have been visible?