There is a strangely prevalent opinion in some circles that everything there was to know about WWII was already known, and that any new information is completely unnecessary revisionism. Those people are naturally wrong, as illustrated pretty conclusively by Yuri Pasholok. Something as fundamental as a measurement went uncorrected for decades.
For instance, if you look up the values of front armour for the SU-122, you'll probably see 45 mm at 50 degrees for the upper front plate, 45 mm at 45 degrees for the lower front plate. This value seems universally accepted, but also wrong.
Both angles are off: the top plate is angled at 52 degrees from vertical, and the bottom is 60 degrees from vertical. This is not just a one-off measurement, and its pretty noticeable in other blueprints as well. A line sloped at 50 degrees is way off on the overall blueprints.
The SU-85 shows the same armour:
The pattern keeps going with the SU-100. SU-100 armour diagrams are closer to the truth, with an angle of 55 degrees on the bottom, as opposed to 60.
This discrepancy is shown not only on paper, but in metal. A measurement of the angle that the upper front plate meets with the roof is pretty clearly 52 degrees on both the SU-100 and SU-85.