[GreenKeys] Strange double plug

[Jim Haynes]

Maybe some of you old telco types will recognize this thing.  I wish we
could attach pictures.

When I bought it on ebay I thought it was an ordinary double phone plug
with a switchboard cord attached.  Now that it's here I see it is
something peculiar.  It was ebay item 140555902416 if you want to go
to the completed auction items and look at the picture.

The plug connects only to the sleeve terminals of the jacks!  The plugs
are solid brass nubs that don't reach far enough into the jacks to
contact the tip contacts.

The origin appears to be Western Union.  I sure can't imagine what kind
of circuit would make use of a plug like this.