I have never seen a coiled trimline line cord. It does appear to have the base connector. I don't know how easy it would be to crimp that on another cord. It is a 5 conductor cord, which is the same # of conductors as the early trimline handset cords. The ends of the cord are straight, which isn't how the ends of a trimline handset cord are.
If it is a real trimline line cord, then It was probably for a 2 line or special purpose set.
If it turns out to be real , then that would be a bonus.
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I think $75.00 is to high for it.
Most of my common trimlines were purchased for $2-$5. I now pay up to $10.00 on a really nice round button set.
I think that phone would go for $30-$40 tops at a phone show.
JMO,
Jim