So what is this chip? Maybe it’s simply four comparators, but they could have a specific purpose. The chip could be a converter for four differential input signals, e.g. DCS (Differential Current Switch) logic. Another chip in the family seems to be Emitter-Coupled Logic, so this chip could be four ECL inverters (but it doesn’t make sense to have four pins for the reference voltage). It’s a bit puzzling that two comparators have inverted and noninverted outputs, while two have single outputs.
See the full post on Ken Shirriff’s blog.