WIldwinds is an ancient coins reference site, a good "one-stop-shop" for looking up any ancient coin. Click on Roman - Imperial Coinage by Ruler", then scroll down the list until you see "Crispus". Then scroll down the list of coins until you see "Rome - RIC VII 180 var." over on the left hand side (this is a catalogue reference number, from the
Roman Imperial Coins series of books). Click on "Image" and you'll see a coin very similar to yours.
The Islamic coin is mid-period, judging by the style of Arabic script; it is roughly contemporary with the Crusades (AD 1100-1300). Probably Seljuq (Turkey), or perhaps one of the petty dynasties from what is now Syria / northern Iraq / southeastern Turkey.
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