Hi Sascha, nice buckle and most of the paint still left on which is nice!
First one i ever saw
I have another exemplar from the Luftschutz, zinc. IŽll make some pics as soon as possible, if required.
Sadly the catch is missing. IŽm not often seen ones like that.
A good pair of SHD's, although it is a slight pity that the Sieper has been essentially stripped of the obverse silver grey paint. Having said that, these buckles are now becoming more and more difficult to find.
The zinc though is great and really, extremely rare. To my knowledge, there is no reference to these zinc SHD's in any reference work and I have have only seen a handful over the years.
Attached are images of the aluminium SHD and which of course is cleverly faked and to a much higher standard than the usual cast horrors. I have also attached images of my zinc example and just to finish off, a steel SHD by Gustav Brehmer.