I've been to Turkey this summer, and I've found five different tokens for public transport in Istanbul:
1 and 2 - Metro-tram and metro (1,75 TL). Both types circulate together, they are equal.
3 - Long distance ferries (3,50 TL)
4 - Ferries inside Istanbul (1,75 TL)
5 - Urban railway (1,75 TL)