In the Ottoman monetary system of the time, there were 40 para to the qirsh (or piastre), 100 qirsh to the lira. Thus your coin is equivalent to 1 qirsh. It says "40 para" rather than "1 qirsh" because the word "qirsh" was only being used on silver coins.
As for contemporary buying power, consider this: in 1878, the British Empire annexed Cyprus from the Ottomans and gave it its own colonial monetary system, which was a hybrid of British Imperial and Ottoman monetary units: there were 9 piastres to a shilling, instead of the usual 12 pennies.
So I would conclude that a 40 para coin had slightly more buying power than a British penny of the same time period. As would befit it's size. "Small change" in the sense that it was one of the smallest denominations issued, but still quite powerful compared to modern coinage. In an agricultural society like Ottoman Egypt, it probably could have bought enough food to feed a family for a day.
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