CASE LAW - R v Song
Mr. En Song received a traffic ticket for speeding in a school zone while traveling down a steep hill. He had some difficulty communicating with the police officer due to language problems. He had asked what his speed was and the officer did not tell him. He paid the ticket in full within 30 days.
On reconsideration, Mr. Song decided that he needed to present his side of the issue in court. Mr. Justice W. F. Ehrcke refused to set aside the guilty plea because Mr. Song did not have a good defence to the charge. The Justice also considered whether the plea itself was invalid, the relevant considerations are whether the accused has shown either that the plea was involuntary or that it was equivocal or that it was not informed.
Isn't it usual ...
... for the officer to indicate on the ticket both the existent speed limit, and the speed of the vehicle within that zone?
The speed zone and speed of the accused are written down in the officer's notes, not on the face of the ticket itself. One can infer the speed range based on the indicated penalty and the driver should know how fast they were driving from paying attention to their speed. That should match the speed communicated by the officer within a few km/h.
Reference the article How Accurate is Your Speedometer?