[old_tv_nut]

This is not for connecting a VTR. It's for changing the time constant in the horizontal circuit to a shorter value to eliminate horizontal "flag waving" (fluttering bending left and right) at the top of the picture when viewing a video tape/cassette.

Pre-VCR, sets had longer time constants to reduce horizontal jitter on noisy signals, but this meant that the possibly huge jump in horizontal sync at the bottom of the video field in a VCR signal would cause a transient that would persist into the top of the following field. The shorter time constant would make the horizontal slightly more susceptible to jitter from noisy off-air signals, but the VCR transient would die out during the overscan period above the top of the visible picture.

This is the first time I've seen a jumper provided to pick the time constant. When VCRs became common, manufacturers just put in the short time constant permanently.