My source on timeline and etymology: Dictionary of coin names by Adrian Room, ISBN 0710206461.
Thanks Peter. Looking at Room's CV I am not convinced he is going to be good on technical numismatics - indeed, I wonder if he has rooted his conclusions in 15th century text at all? Is he just compliing other peoples 19th and 20th century whims?
That the Ottoman akche is ultimately a weight reduced Ilkhanid double dirhem is an idea I got from Steve Album - private converstion back in the 1980's. Looking quickly through his Checklist edition III I see he mentions this matter in connection with Eretnid silver (pp 250-51).
That the Genoa AR's are to the Golden Horde dirhem standard just seems the best bet on the basis of the coins themselves - see Mitch Islamic (p. 320). MM seems to agree and calls them "dirhem" and "denga"
But this is not a matter I investigated much, so would welcome comment.