I had an early VCR that ignored the Macrovision stuff when copying tapes. The Macrovision code was copied along as a relative borrowed one of my copied tapes and the code messed up her taping it.
I remember those days. Several early VCRs were immune to Macrovision because they had
intelligently designed AGC circuits -- circuits with attacks and releases and gating thresholds that allowed excessively bright
areas of the video to simply clip rather than triggering the AGC to reduce gain on the whole video signal. I.e., their AGCs were designed so that only pictures that were excessively bright
overall would trigger gain reduction. The pulses of above-100 IRE video that Macrovision embedded into the VBIs of its protected tapes would sail straight through those circuits without causing them to spasm, making copying a breeze.
Believe it or not, Macrovision's people responded to the existence of those well-designed VCRs by making deals with (paying off) manufacturers to use simpler AGC designs in all future models that
would react to Macrovision's >100 IRE pulses. Those simpler AGC circuits effectively behaved like stupid simple 1950s audio limiters that ducked on everything, even brief transients.
Every now and then, even into the 1990s, occasional VCR models would appear on the market whose designers employed proper, old school AGC circuits. People would be able to use those models to freely copy their protected tapes without the use of Macrovision stripping boxes. But as you experienced with your vintage model VCR, the >100 IRE pulses buried in each protected tape's VBI would go along for the ride, and "lie in wait" to frustrate any future copying attempts using "lesser" (most) VCRs.
