Was there a certin date they started putting the numbers on the backs of these coins? (On bottom) I am guessing the numbers on the backs of these coins refers to the amount of coin worth? XX10=10asses???
Those appear to be mintmarks. However, the XXI is thought to be a base-metal to silver ratio; this is commonly seen on coins bearing the image of Aurelian.
1. XXI = metal ratio 2. rSIS(symbl) Third Officina of the Siscia mint. Not sure what the last symbol is. 3. XXI = metal ratio. The V above the XXI is unknown. 4. --SIS. Siscia mint, can't tell the officina.
I have these two coins in my collection. The attached photos are from the RIC reference pages. XXIP and XXI are implied to be Mint Marks. Probus. AE Antoninus. 276-282 AD. Cyzicus. IMP CM AVR PROBVS PF AVG, radiate bust left wearing imperial mantle, holding eagle-tipped sceptre SOLI INVICTO, Sol in spread quadriga facing. CM in lower centre. Mintmark XXIP. RIC V-2 Cyzicus 911. Probus AE Antoninianus. Siscia mint, 282 AD. IMP C M AVR PROBVS P AVG, radiate cuirassed bust right RESTITVT ORBIS, Woman standing right presenting wreath to emperor standing left, holding spear; P between, XXI in ex. RIC 713 var. (officina letter and obv. legend with P AVG)
http://www.forumancientcoins.com/dougsmith/feac73xxi.html http://www.forumancientcoins.com/dougsmith/officina.html My pages above cover XXI and officinae. It is good to remember that mints were free to do these things 'their way' so there is no single explanation to the matter. XXI meant a ratio of 20 parts base metal to one part silver using Roman numerals. Some mints preferred to use Greek so XXI became KA for twenty and one. This works out to about 4.7% silver since the Romans did not say one part in 20 but said one part added to 20 which we would say 1/21. I believe the 'O' is actually a Q standing for the quarta (4th) officina. Whenever you show a coin asking for help, it is best to show both sides. If nothing else, that would help people not familiar with the coins to learn who issued which ones. More than one mint and more than one ruler used Clementia Temporum. Specialists will know what was on the obverse of each of your coins but some of us are not that far along in our journey. Below is a 20:1 expressed KA. In this case the B means officina two. The obverse shows Florian.