[R-390] grease

[Andy Jackson]

For decades, electro-mechanical telephone exchange equipment (Strowger, or
Stepper in the US) used a product called "Oildag" which was a suspension of
graphite in oil. This was used in areas where one metal part impacted on
another - ratchets, pawls etc, and providing it wasn't applied too
liberally, stayed where you put it.  This was usually in close proximity to
open relay contacts and mechanically operated contact sets and it was
normally applied as a drop with a small artists brush.  The great benefit
was that even after the oil component dried out, the graphite continued to
lubricate.  The disadvantage was that the graphite did produce a rather
messy appearance.
In the 1970s it was replaced in the UK at least by a specially formulated
oil to which a "stickyness agent" had been added but general opinion was
that it was never as good as the old Oildag.
Unfortunately, modern exchanges don't require any oil at all - except maybe
on the main door hinges!

73,
Andy G8JAC