Without an operational specification plate or identification on the press you don't don't what you have.
When you disassemble the hydraulic cylinder you can then measure the bores, o-rings and packings and get a better ideal on what you have. I doubt the hydraulic cylinder is custom.
Engineers Edge has cylinder force calculators
http://www.engineersedge.com/calcula...calculator.htm
http://www.engineersedge.com/calcula...calculator.htm