Thanks a lot there. Those pictures really help with getting the look and feel right. Meanwhile, going through some old books I've found this, thought I'd throw it out there if anyone needs a bit of reference.
As you'll probably see, the author calls it a Vacuum lubricator, but as far as I can see, it works as a displacement lubricator. Steam goes in at
g, then condenses to water in
p, pushing the oil contained in the reservoir up into the J-shaped tubes from where it goes into the sight glasses, which have regulating knobs attached. It's quite similar to the one you've shown, except some small differences.