By the way: I can recommend the 1st edition of the Hensoldt History. You will find the very first Hensoldt binoculars and a lot of other interesting details. The book is in German. I think that you can get copies from Deutsche Optik.
Porezag, Karsten. Hensoldt: Geschichte eines optischen Werkes in Wetzlar. Band 1: Familien- und Gruendungsgeschichte bis 1903. Wetzlar: Karsten Porezag, 2001. 448 pp.
D.O. is selling this for about $50., and it is a very fine book; volume 1 of a future three volume set. There is much on Hensoldt's first binoculars. --Peter
Subject: 'Old Naval Binoculars' question.
From: hans.t.seeger@___ne.de (Hans Seeger)
Question “Old Naval Binoculars” by Harry Cavanagh. The glass in question is a 10 x 80, 20°. Some versions and details on the construction can be seen in my book on pages 354 to 358 and on page 251 (Kevin Kuhne’s chapter in English). Stephen Rohan has depicted this glass on page 105 and the following pages (Eyes of the Wehrmacht). If this glass was made by Zeiss you will find the serial number on the lower side of the cast housing. Please inform me about this number.
I can enlighten a little meagre bit on Hensoldt binoculars.
On june 13th. 1905 A letter says that according to the danish representative of Hensoldt in Copenhagen, one Lt.Col. Pade, Hensoldt will in the near future be delivering a new design of binoculars, without mirrored prisms.
Presently, The latest deliveries from the company has been manufactured of steel! Instead of Aluminium.
The reason for this is, that the oxidation of the aluminium parts in the binos deteriorate optical performance!
The surfaces of the prisms gets coated with oxidations products from the aluminium.
Does anyone know what this means?
Apparently it is NOT the silver mirror surface, that deteriorate.
And the new design mentioned, must be the first true Dialyts.
The flawed design mentioned above, is the old type with flat oval prism housings.
Has anyone seen one of those, made of steel?
Or maybe the steel design is the type with only objective and ocular openings in the prism house casting?. ( but still retaining the silver mirror prism system)
Later, in early 1906, the same representative confirms that deliveries of the new straight through design has been made.
Unfortunately there is no reference til serial numbers.
If this should be said in short, then:
Alu oval prism house binos up to around 1904-1905
One piece prism houses of steel 1905-1906
One can speculate, that the idea of the one piece casting prism houses are caused by moisture in the old screw assembled oval design.
It may be a neccessity in order to make the silver mirror prisms work well.