Was there a standardized test to measure [print-through]?
I believe so but the problem, as I recall, was that the subjective annoyance of print-through was entirely dependent upon the nature of the programme content. The fact that neither the frequency nor level response of the print-through were linear, whether the tape had been stored tail-out or not (making the worst of the print-through a “post-echo” rather than a “pre-echo”, generally thought of as less damaging but on a simple speech recording, probably no better or worse) all contrived to make measurement of print-through a largely academic exercise.
Some tape types had a reputation for being prone to printing, others didn't. For the work I was doing at the time, we didn't loose too much sleep over what the print might be like in a few years – it was what might happen within a few weeks that mattered. Print-through, being within the “Dolby loop”, was typically reduced by about 10dB compared to non-Dolby recordings and most back-coated tapes seemed to reduce the phenomenon to manageable levels. It was a far more significant problem in the film world where the use of small spools of long-play (thinner), non back-coated, tape stock was common.