I shall check out the trigger calibration but shall focus more on aesthetics.
The tunnel diode based trigger circuits used in these oscilloscopes tend to drift a little over time compromising performance. The trigger calibration procedure does not require any special test equipment and is easy enough so it is well worth doing if a problem is suspected. If there is a real problem with the trigger circuit, then there is a good chance that the trigger calibration procedure will reveal it.
My notes say that all of the 475, 475A, and 485 models used tunnel diode based trigger circuits. The 100MHz models like the late 464 and 466 and all of the 468 units used integrated triggers but I think at higher speeds it was easier for Tektronix to stay with the tunnel diodes.