So that's why a 2 systems were getting crappy speeds. Yes, 2. It had been used only to split a single drop from another switch between two systems.
New drop, happy clients.
Some stuff here is museum material.
I guess that's what I haven't figured out yet - it's about 200' and I don't have 200' of wire laying around. I'm thinking of making dummy terminations for each end of my cat6 cable and stripping each of the pairs and twisting them together so it works as a single conductor and using that to measure.