> Does any body know where Rios block at mp 192 on coast sub came from?

I think you might have your terminology mixed up. If there was a "Rios Block", that suggests it was the name of a DTC block (or maybe even BRT). The Coast line was ABS-DTC in late SP days.

UP doesn't seem to care for DTC which uses fixed limits of a "Block". So if you're talking modern era, "Rios" would either be a Station or a Control Point (in CTC or an interlocking), as TWC uses established locations (typically a Station, Switch or MP) to establish the extent of its limits.

Of course, you may have heard someone else incorrectly (at least per actual rule) apply to ask the DS or the DS reply getting them to that "block", which is just their reference they need the next bit of track to Rios station (official or unofficial?).

I would be curious to known, but I'm not familiar with the current Coast line operations. Didn't UP change it from DTC-ABS to TWC-ABS not long after takeover? Plus a few islands of Double Track w/ or w/o ABS? Has any of it been upgraded to CTC?