I bought my two slugs from a G.C. auction slabbed because they were the 1st identifiable hoard coins in my collection . In regards to the hoard, 49 coins of Valens were recovered from the Rome mint, & 58 from the Lugdunum mint. Over 700 coins of Julian II were recovered from the hoard (285 from the Ludunum mint).
The two annulets from between the borders of the diadem look like they might be jewels like in the example I posted. A plain pearl diadem has nothing between the rows of pearls.
Jullian II AR Siliqua Struck as Caesar 357-360 CE Constantia/Arles mint. Obv: D N IVLIANVS NOB CAES legend with bare-headed, draped and cuirassed bust right. Rev: VOTIS / V / MVLTIS / X legend in four lines within wreath; mintmark TCON below. 2.01 grams. Found Sparle, Norfolk. RIC viii, 263-265; RSC 154b; Sear 19046.
Great Siliqua's @Bing and others. I do not have late silver coins like yours, but I did win a scale weight in a recent auction that is part of a similar bronze coin. The reverse inscription is on several coins. I do not recognize the bust. Byzantine Weight, Circa 5th-7th centuries. Weight of 1 Nomisma (Bronze, 13x13 mm, 4.33 g, 6 h), a square coin weight for a solidus made from a 4th century follis. Pearl-diademed, draped and cuirassed imperial bust to right. Rev. VOT V / MVLT / X within wreath. Very fine. This weight was made from a follis dating to the 360s-370s, perhaps of Jovian or Valentinian I.
Have you weighed it? At 4.33g it seems mighty heavy for a piece cropped from a coin that was whole about 3 to 4g at best. I doubt that this piece is that heavy. The original coin was likely minted for Jovian in Rome (MV dot LT is a characteristic for the votive coins of Rome in the early to mid 360s, both AEs and siliquae), possibly RIC Rome 333/334.
Here is Julian from Lugdunum: 17 mm. 2.05 grams. FL CL IVLIA-NVS PP AVG VOTIS/V/MVLTIS/X in wreath LVG RIC VIII Lyon 219 "Spring 360-26 June 363" This is a "reduced siliqua" when Constantius II was still recognized, so the end date is earlier than the one given. Look at the flans and weights of the previously posted siliqua of Julian. Most are clipped and lighter weight. It is very common for siliquae to be clipped. One theory about that is that the official weights dropped over time and those that had been issued earlier and were still around had more silver which was extra considering the new lighter official weight, so the old ones were clipped down to the new weights. Of course, that does not rule out people just shaving a bit of silver of the edge and hoping to pass the coin anyway. Any of his silver under 1.8 grams is probably clipped.
Mine weighs 2.2 grams but has no dots around the border, so I have to think that it was probably clipped a little bit as well.
As a followup to my post above, here is a Valens siliqua which has obviously been clipped: 15 mm. 1.43 grams. DN VALENS PF AVG VRBS ROMA Mint mark TRPS King noted over 300 pieces with very similar clipping in a hoard in the Preston museum (NC 1981, well-illustrated on plates 13-20).
Arcadius Arcadius, AD 395-408 AR Siliqua, 16mm, 1.1g, 12h. Obv.: DN ARCADI-VS PF AVG; Pearl diademed, draped, and cuirassed bust right. Rev.: VIRTVS RO-MANORVM; Roma seated left on cuirass, holding Victory on globe and reversed spear. Mint MDPS, struck in Milan in 402, Ref: RIC1227 From the Doug Smith Collection, #2829
I will continue to maintain that terms like rosette and pearl diadems is an attempt by scholars to force many things into a few categories for the sake of their system. Each mint and each cutter had the option of rendering a model as they saw fit. What looks like a rosette at one might not match the others. My example below is obviously pearl and shows two strands of small dots. I see that as the edge view of the central medallion more often shown unnaturally turned to the side so it shows on the coin. The question is whether Bing's coin has tiny rosettes or is just an intermediate variation showing the die cutter did not know 20th century students would expect him to cut from their list of options. This is a distinction for specialists who value these modern attempts at classification more than I do. Some series of coins assign new numbers to things like this while others lump them all into one group. I will value the terms more when they are shown to represent something meaningful like the difference between Consular and Military attire and not just a question of which piece of jewelry the die cutter liked that day. Such questions are interesting to some and some even pay extra for such minutia. I see it as studying the book rather than the coins so I do not compete with those who worship the book. It would be interesting to see if there is a coded meaning to the diadems. Might they relate to a change of weight standards as did the drop from two standards to one in the common GLORIA EXERCITVS coins? That would provide a good reason to separate the series.