AH and regnal dates

[oldecurb]

For most (?)  countries I understand that the actual date of coin issue is the AH 4 figure date plus the 2 figure regnal date.  However for some the regnal date is ignored.  This came up in a discussion about a Sudan 20 piastres (KM 26) AH1312/12 where I believe the 4 figure date is the actual date. In Krause I see it was issued in AH 1312/12, 1312/16, 1313/13, 1315/8 and 1315/12. So if the regnal date doesn't affect the date of issue why are there these variants?

Question 2 - Is there a rule of thumb about which countries ignore the regnal part of the date?

[capnbirdseye]

I'm not sure how there can be AH 1312/12, 1312/16, 1313/13, 1315/8 and 1315/12, the regnal year means counting from the accession of the monarch starting with year one  or ahad, so those regnal years don't make sense to me as they are not consecutive but it not uncommon to see such iregularities on Islamic coins

[Afrasi]

Usually on Sudanese coins the "reignal year" repeats the accession year,  but some show the correct accession year of the Khalifa, a few refer to the accession year of the Mahdi, some have errors confusing "5" and "0", and some ... some will drive you crazy, if you try to understand them.
In these times and this area there were not only artists working in the mint of Omdurman.

On Darfur coins the accession year is usually "17" regarding the accession date of Ali Dinar, but sometimes occurs also "71", the accession date of Ibrahim Muhammad Hussein al-Mahdi, his grand father, the last Sultan of Darfur.

So the thumb rule is: In the hardest times in the poorest areas nobody cares about correctness of letters and numbers on coins.

[FosseWay]

Ottoman issues of Qstantiniyah (Istanbul) and Misr (Egypt) always follow the fixed accession year plus 1 or 2-digit regnal year pattern. You have to remember that reigns do not include a year 0, so when calculating the actual Hijra date of a coin, it is accession year + regnal year -1.

So coins of Sultan Mehmet V's first year, inscribed with accession year ١٣٢٧ (1327) and regnal year ١ (1) belong to a year beginning in Hijra year 1327, not 1328. If you do the conversion to AD: (1327 x 0,97)+622 you get 1909, which is indeed when his reign started.

As to determining in the case of other issuers' coins whether the four-digit date is a regnal year or a 'real' Hijra date, probably the best solution is to look up the ruler in question on e.g. Wikipedia and match his accession year with what's on your coin.