In message , at 21:35:22 on Mon, 16 Aug
2010, Roland Perry remarked:
No, I seem to remember that they were about the same height as your
standard pillar postboxes -- perhaps slightly higher.

Sorry, I wasn't clear -- I mean shallow depth, not height.

The window is fairly flat, which reduces the depth a bit, but doesn't
have much impact on the volume.

Here's a picture of one, that blows my mental image above (which would
be that sort of footprint but reversed Flat windows, kind of, but
three of them...

http://www.flickr.com/photos/10951875@N07/2468901964/
--
Roland Perry