Originally posted by Lusche
I don't know for allied tanks, but to my knowledge neither Panther nor Tiger tanks had rangefinders.
There were some converted Beobachtungspanzer V, (observing tanks), Panthers without a cannon but with a rangefinder.
The planned Panther Ausf. F and the Panther II would have featured a new turret "Schmalturm" with an integrated stereoscopic rangefinder.
Well they had rangefinders. Not in a sense like steoroscopic or anything fancy, but stadiametric RFs. On the Tiger and Panther, IIRC also on the Panzer IV, they had a big aiming triangle (and a few smaller triangles to the sides for leading) which had the width of 2 mils (Strich). A tank usually has a width between 3 and 4 meters headon, and a length of 6-7m.
Knowing that you could use regula tri (Dreisatz).
After that you set the range into the gunsight, put the tip of the triangle on target and hit (or miss, based on your ability to judge).
Matt