I was searching for maximum speed from freight wagons build before 1900 and i found nothing, really not one note.
An i am wondering. Why did the Prussians not find it necessary to state the maximum speed of the wagons in their standard plans?
The reason: everyone knew the official regulations. And the maximum allowed speed, all wagon can drive without problems.
Rail accident at Hugstetten 1882
https://de.wikipedia.org/wiki/Eisenbahnunfall_bei_HugstettenCause of the accident
Brakes had been assigned to six of the 28 cars. Since the train had been released for general traffic for the return trip to Colmar, two of the brakemen took care of collecting the fare after the start of the journey. Another brakeman was busy instructing a new colleague. The other two did not have sufficient knowledge of the route, so that one did not brake in the decisive downhill, the other too weakly. So the speed of the train increased due to the weight of the pushing railway wagons. The locomotive started to "rock" and put an intermittent load on the inadequate superstructure, which could not compensate for this. The locomotive staff tried to brake the locomotive and tender - to no avail. At an excessive speed of approx. 70 km / h - speedometers for speed control were still unknown - the KNIEBIS derailed and got stuck in the swampy terrain.