This is an original two-nipple 12528777 coolant recovery tank that I personally removed from a 1994 Buick Roadmaster (the original applications include 1994 and early 1995 GM B-bodies) that I found in a local wrecking yard. It's in really, really nice condition with just a little yellowing around the ports. I cleaned out all of the sludge and tested the switch with an ohm meter to confirm that the resistance changes as the float moves - it does. I'm pretty sure that means the switch is working properly, but I haven't installed it for an in-car test.
This two-nipple tank is an obsolete part that's no longer available from GM. If you're looking for a good, used original part they don't get much nicer than this.
Please note that GM now uses the 1252877 part number for the single-nipple coolant recovery tank that was originally used on late 1995 and 1996 B-bodies. The original late 1995/1996 part number was 10273298.