I just realized all these samples of gold solidus of Constantine I are forgeries, struck by modern dies.
Constantine I, Solidus, Treveri 310-313, AV 4.46 g. CONSTAN – TINVS P F AVG Laureate head r. Rev. S P Q R OPTIMO PRINCIPI Aquila between two standards; in exergue, PTR. C 556. RIC 815. Alföldi 507. Depeyrot 17/9.
NAC 54-613: https://www.acsearch.info/search.html?id=758841
Gorny 159-474: https://www.acsearch.info/search.html?id=404596
Hess Divo 317-915: https://www.acsearch.info/search.html?id=875590
The dies have been recently published by Dr. Ilya Prokopov on “COUNTERFEITS OF ROMAN AND BYZANTINE GOLD COINS – Revealing the secret of how they are made.” (Sofia, 2015), p.32, No.3.
Citing: “Specific features: Obverse – smudged letters on 9h (PF); Reverse – short positive line between the letter P and border of dots on 2,5h.”
Dr Prokopov published as sample of struck forgery the NAC specimen, but tonight I realized that also the other samples from acsearch are all fakes.
IMHO the fourth and last sample from acsearch could be the genuine prototype inspiring the forger: Auctiones GmbH E27, lot 59: https://www.acsearch.info/search.html?id=2026414
This is the one for sale on the bay (4.3 g, 17-18 mm):