[Leica] Info on "new" lenses?

["Zeanah, Derek" <DZeanah@alston.com>]

Just purchased an M4-P and a couple of lenses (35 Summicron, 90 Elmarit)
from LUG participants, and I couldn't be more pleased with the
equipment.  I do have some questions on them though.

The 90mm lens is black, s/n 2,721,xxx, and says it's a LEITZ WETZLAR
ELMARIT 1:2.8/90.  The lens says GERMANY on the base of it, and
distances are listed in feet and meters, though the M (for meters) has a
sideways 05 next to it.  It has a clamp-on lens shade (IUFOO), but I
can't tell that the head detaches.  Am I right to assume that this is
the "original" Elmar (as opposed to the "thin," "thick," and "Elmar-M"
varieties) from around '74?  Can you tell me what size filters this
thing takes?  What size lens cap would the hood take?

Any "Gotchas" about this lens model?