Jeff Laurence said:
...The copy I have of The Letter, by the Boxtops is worst...
My memory on this topic is blurred by the fact that some songs were more prone to have noticeable cueburn because of low levels on the intros. "The Letter" started with three snare drum beats well below the level of the rest of the recording.
Robert Flack's "First Time" had a similar issue. It's hard to get good signal-to-noise ratio when the signal is weak to begin with.
When I play a 45 now, the thing that jumps out at me is not so much the cueburn, but the wow. Tolerances on centering the grooves on the hole must have been pretty loose. (But I recall Motown being really good on that, too.)
I remember putting 45s on the Technics turntables without the 45 adapter, holding my thumbnail to locate the point and distance of maximum offset, sliding the 45 from that point toward the center by half the distance of the error, and locking it down using the spindle clamp from an ITC 750 tape deck before carting it up. It was odd to see the record wobbling off-center, with the tone arm holding perfectly still, but it got rid of much of the wow.