Thanks for the thread Jeff - I wasn't going to post anything for another week or two as I'm cameraless, so I only have the telephone, but here goes...

I've always liked this family, right from the early Leonidas, through the standard Bunds and on to the Tutimas of more recent times. In amongst this large family there are the oddities of course, the Heuer Cal 12 prototype Bund that never was is probably the rarest of them. Next up is probably this variant of the standard Heuer 1550 Bund, it is the Sternzeit Reguliert version, the 1551 SGSZ, issued to artillery units in the early seventies as an astro-navigational chronometer. It originally came in a leather case with a star chart and notes, but I don't have that at the moment.

'Sternzeit Reguliert' translates as 'Regulated to Sidereal time' which runs about 4 minutes a day slower than local time. This was to assist in theodolite sighted position-fixing by the artillery units (it's important to know where you are so you know how to far and in what direction to lob your shells).
Mine has been regulated to run at a normal rate; 18,000bph in the case of the Valjoux 230 movement that runs it. The movement itself is a good one, based on the Valjoux 23, manual of course, column wheel and fly-back.

The lever towards 11 o'clock, near the column wheel, functions the fly-back:

(Courtesy Alan Cook)

The unique NSN for the Sternzeits -

Flush, nicely bevelled crystal:

Next to the similarly cased Sinn 156:

And the backs - notice the slightly asymmetric pushers on the Valjoux 230 as opposed to the Lemania 5100 and the difference in caseback depth between the manual and auotomatic:

Anyway a brief look at an uncommon variant on the Bunds, I guess about 100-150, possibly more, but you don't see them for sale very often. Some of them changed dials at service, but the NSN and 1551 SGSZ engraving between the lugs are unique to this model.

Anyway, I would recommend Richard Askhams site for excellent details on the movement - http://thewatchspotblog.com/?p=922 and Walter Mannings site for 3H Bund variant information - http://brown-snout.com/horology/articles/heuer_bundeswehr_chrono/ then of course Dr Konrad Knirims extract - http://www.knirim.de/heuerbund.pdf for excellent background and technical details. (I was in touch with Konrad about production numbers and he already knows about the discrepancy of course :thumbup: ) and finally Daves thread comparing the two models in much deeper detail - http://forum.atgvintagewatches.com/showthread.php?t=621

So, not a Lemania for a change for me, but it's a refreshing change nonetheless.

Here on an extract from the LRDG manual, giving interesting background on the same navigational technique:

Cheers,
Andy