547
The 547 is a 50MHz scope that takes letter-series and 1-series plug-ins. It has two identical timebases and it has the ability to display one input with one time scale and another input with a different time scale. The effect is similar to a dual-beam scope. This "Sweep Switching" feature differentiates the 547 from the 546. Triggering is done with tunnel diodes, which tend to shift in characteristics as the instrument ages.
A replacement CRT for the 547 can be taken from a 543B, 544, 545B.546. or another 547. A common problem with 547's is the HV transformer. When it fails, typically it overheats. The usual solution is to scavenge a replacement from another scope.