This coin (pendant) is currently on offer on a Ukrainian auction website. Terrible condition, but what a rarity. The piece was found in the Rovenskaya Oblast'. The price is currently around USD 30,- and I don't think it is going much higher. In good condition, this piece can cost a quarter of a million, but, as I always say, condition is everything. Show your Constantine I silver medallion with military bust three-quarters facing - just kidding.
Curiously enough, this is the second piece that I have seen being auctioned on this Ukrainian auction site. The other one was sold a few years ago. It was also badly worn, but not broken. I suppose they were popular with East Germanic people who lived in the area at the time and who used them as pendants.
At 3.5g I would assume it is a clever fake. Almost half the weight of a true medallion. Maybe @Victor_Clark can chime in.
Yes 3.49 grams is way too light. I hadn't noticed the picture with the medallion on the scales. I found a picture of the other Constantine medallion, that was sold on the auction site in 2017. That piece weighted 5.04 gr. (including a loop). Maybe these are very elaborate fakes. I don't know. The broken one that is currently on offer seems to go for USD 32. The one below sold for USD 115.
Here is the Constantine medallion, which was sold sold in 2018 by NAC, for comparison. It has a lot of excess metal, suggesting perhaps that weights of maybe 4 to 5 grams could be acceptable as well.
I saw one of the originals in the coin cabinet in Munich (Germany). This maybe the piece, but I am not sure.
The extent of the loss of metal on the pieces from Ukraine is obvious when you compare the position of the horse's mouth. On the pieces from Ukraine the mouth is slightly cut off, while on the other coins there is a good deal of distance to the edge, including what looks like a thick rim. In addition, the image of the Lupa with Romulus and Remus on the shield is completely worn off on the Ukrainian pieces, indicating that a lot of metal has been lost from the overall surface. I suppose that this could explain the large weight discrepancy.
But you also have to consider that the additional weight of the loop is included in the total weight of the Ukrainian examples. So the weight of the coin is even lower. One possibility is that the Ukrainian pieces are not original medallions but rather old jewelry pieces copying the medallions.
Yes, that is a possibility. From what I can make out on these badly worn coins, they look official to me, but it is hard to tell.