Quote:
I'm guessing on the denomination because my Krause does not give a diameter (a 5 piastres would be 20-21mm) and I can't clearly see the denomination below the toughra...
I can... I can just make out the "10" beneath the toughra. A 10 piastres it is!

And to clarify: Year 8 is the regnal year, but the actual date on the coin is AH 1310, equating to AD 1892. On coins of Mahdist Sudan, this given date is the actual date the coin was struck, rather than the accession year, so you don't have to add the two numbers together like you do on Ottoman coins.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis