I feel like for the entire time these were on circulation the silver wash would have been very strong and quite evident; I feel like the public would have seen gleaming “silver” coins all the time
GALERIA VALERIA AE Follis OBVERSE: GAL VALERIA AVG, diademed & draped bust right REVERSE: VENERI VICTRICI, Venus standing facing, head left, holding apple upwards and raising drapery, star left, HTA in ex Struck at Heraclea 309-10 AD 4.8g, 29mm RIC 43 CONSTANTIUS I AE Follis OBVERSE: CONSTANTIVS NOB CAES, laureate head right (large head type) REVERSE: SALVIS AVGG ET CAESS FEL KART, Carthago standing facing, head left, in long robe, holding fruits in both hands. Mintmark Gamma Struck at Carthage 298-299 AD 7.41g, 28mm RIC VI 32a
Maybe, but I have seen many more well worn folles with no silver showing on the surface than ones that are gleaming with silver. But, it is possible that the silvered coating on these dark coins simply faded with time and had remained silverish while in circulation. It would be nice if we could see the appearance of ancient coins as they appeared at that time.
You can find them, but usually the silvering has a patina. This one has been cleaned at some point and is looking minty, almost 90% silvered. Diocletian A.D. 298-303 27x29mm 9.3g IMP DIOCLETIANVS P F AVG; Laureate head right. SALVIS AVGG ET CAESS FEL KART; Carthage standing facing, head left, holding fruits in both hands. In ex. A RIC VI Carthage 29a/31a