The highest score I've come across for verbal and quant is 51. This score is so high that GMAT does not distinguish it from the theoretical top score of 60.
So you can think of 60 as the theoretical max and 51 as the practical max.
"Wherever you go, go with all your heart" - Confucius
1. How to Review and Analyze your Mistakes (Post by BB at GMAT Club)
2. 4 Steps to Get the Most out out of your CATs (Manhattan GMAT Blog)
My Experience With GMAT
1. From 650 to 710 to 750 - My Tryst With GMAT
2. Quest to do my Best - My GMAT Journey Log