NavList:

K McGrath wrote:

"The top left hand corner has a padded semi cylindrical moulding in line with the hinge line. The lid has a corresponding padded block which locates on the semi cylinder when the box is closed. [ ] I'm completely stumped as to what its purpose is. [ ] The only thing I could think of was it's to stop the sextant being stowed away with the shades in the wrong position."

The box for my Freiberger sextant (serial number 840 868) has the same semi-cylindrical moulding (actually, more like a 3/4 cylindrical moulding) that you describe. I think that your assumption is correct; it seems to be there to prevent closing the box with the index mirror shades in the wrong position. There isn't an equivalent device to prevent closing the box with the horizon mirror shades in the wrong position; the box can't be closed unless they are removed fom the optical path of the horizon mirror.

The styrofoam-lined box that Werner Luehmann shows in his post has a different, newer, design.  As he points out correctly, it was made for a sextant manufactured in the 1990s - the first two digits of the serial number are correlated with the year of manufacture. For my my sextant, the year is 1984, as indicated in its calibration certificate. It was therefore made in the last few years of the late, unlamented, German "Democratic" Republic (DDR). It's a curious fact that when a nation uses the word  "democratic" in its name, this does not necessarily imply that it is a liberal democracy.  The German "Democratic" Republic was a puppet state of the USSR, and North Korea, the so called "Democratic People's Republic of Korea" is another excellent example of this paradox.

Regardless of these somewhat irrelevant considerations, the Freiberg drum sextant (Freiberger Trommelsextant) was, and still is, a very well made instrument. The firm Freiberger Präzisionsmechanik continues to manufacture it, which means that spare parts may be obtained if necessary. If you are planning to rebuild yours, you will find the document "The SNO-T sextant (with notes on the Freiberger drum sextant)", by Bill Morris, an invaluable resource. There is a link to Bill Morris's sextant blog in the "Resources" menu of The NavList home page.

Best, RafaelC