They made 2 versions of the cooler one with 2 heat pipes on each side and one with 4 heat pipes on each side that will matter.
The pro 4 is a low budget board so not the best for overclocking but the 2500K usually overclocks easy.
Depending on the cooler and how good of a chip you got probably in the 4.0 / 4.2 area with the cheap (2 heat pipes) cooler and might get 4.4 /4.6 area with the better one.
They all overclock different so that could vary.
Back when I used mine I could hit 5.2 on water cooling using a Z77 Extreme 4 board.
EDIT I bought mine new with a low budget GB Z67 board and clocked it to 5.0 day 1 then after about 3 years the board started acting up so bought the Z77 and got it to 5.2 few years later it became...