Rich Grise writes:
2 5/8" long? That's some BIG keyholes!

These are keyholes for warded locks, not cylinder locks. The hole has
to be big enough for the wards to fit through, and is typically on the
order of 1/2 inch high. The widest part is the shaft hole that someone
might look through, which from memory I would say is around 3/16 inch
in diameter. And the hole in the cover plate is often made larger than
the internal hole in the lock mechanism.

As to the cover, you want it to work so that when you push it aside to
use the keyhole, you push more or less horizontally and only a little
upward, so it swings back but not too readily. To implement that, the
cover is pivoted at a point some little way above the actual hole. See:

http://www.antiquehardware.com/image...0038909-lg.jpg
http://www.historichouseparts.com/images/VH0324-02.JPG
--
Mark Brader, Toronto "But I do't have a '' key o my termial."
-- Lynn Gold

My text in this article is in the public domain.