Then I saw this.
It's an old T-mount Vivitar preset, a 180mm f/3.5, that comes with a MD adapter but of course can use my K adapter. It is small but Very dense at ~635g, apparently made by Tamron a long time ago. It uses 58mm filters and hood that I already have for the 55-300. It also looks like new despite being just a few years younger than me, introduced when Kennedy was President! Soligor also made a 189/3.5, but it looks a lot different.
So it fits well with current gear and fills the prime gap between 100 and 400mm with a unique instrument. Why not bid?
My bid stood alone so it was a bargain that will arrive soon. I look forward to giving it a try!