I'd also be interested in people's practical experience using both the delayed timebase and the vernier control.
The oscilloscope operators instruction manuals for the 475 and 2213 (as well as The XYZs of Oscilloscopes) have some discussion of how to use the delayed timebase to perform different measurements, but I've had trouble wrapping my head around the discussions without concrete examples to try out myself. Here is the discussion on page 29 from The XYZs of Oscilloscopes (1981, for the 2213, which has neither a full dual timebase nor a vernier for the delay):
"Dual time base scopes offer you all the measurement capabilities of single time base instruments, plus:
• convenient comparisons of signals at two different sweep speeds
• jitter-free triggering of delayed sweeps
• and timing measurement accuracy of 1.5%
Most of this increase in measurement performance is available because you can separately control the two sweep speeds and use them in three horizontal operating modes. These modes — in a 2215 — are A sweep only, B sweep only, or A intensified by B as well as B delayed. The HORIZONTAL MODE switch controls the operating mode and two SEC/DIV switches — concentrically mounted on a 2215 — control the sweep speeds.
When you use the ALT (for alternate horizontal mode) position the HORIZONTAL MODE switch, the scope will display the A sweep intensified by the B sweep and the B sweep delayed. As you set faster sweeps with the B SEC/DIV switch, you'll see the intensified zone on the A trace get smaller and B sweep expanded by the new speed setting. As you move the B DELAY TIME POSITION dial and the change where the B sweep starts, you'll see the intensified zone move across the A trace and see the B waveform change."
My father replaced a 475 (which has a vernier) with a 2213 (which has merely has a blank knob) as his daily use scope in the early 80s, after having used the 475 for 6 or 7 years. He had the choice between the 2213 and the 2215 (which has a proper dual time base and a vernier to control the delay) so I can only conclude that he didn't feel that those features were useful in his work (he was a service technician working on laboratory mass analysis equipment — mass spectrometry, spectroscopy, chromatography — and the computers that were connected to that equipment).
-- Jeff Dutky