OS?
Oh, ***** ! ( S H I T E as we said in Scotland)
or
Old Style! or Original Style!, most likely?
They install OK (54/55)
They might not have been cut well on the sides.
The will shrink, or most likely deform, due to humidity.
Seal the back and sides with epoxy primer (or, any other other water-proof primer/paint).
Your first interpretation of OS would be correct. I painted the back side of mine, but it still deformed to show huge gaps on the sides. Deformed is a better description than shrunk.
Carl
