At average weights we found that the Electra would climb well at 250KT up to about FL120 when it hit 500ft/min then i would peg V/S untill the speed came back to 210 KT and at was as high as you would want to go on a short leg , after an hour or so a step climb might be in order ,I am left to speculate that the reason that the older turboprops used about 210 KT was to fit in with the piston engine traffic of the day.
As a comparison the B737-800 econ climb speed is about 300KT.