The horn shown above is one of only a few extant examples of the first full double horn by Firma Ed. Kruspe based on the company's utility patent of 1897 described in  D.R.G.M. 84 240. ¹   It was designed by Fritz Kruspe, son of the founder, Eduard Kruspe, and Edmund Gumpert,²  Two years after the announcement of the invention of the double horn, noted horn historian Hermann Eichborn wrote an extensive article in Zeitschrift für Instrumentenbau describing the general history of horn leading to the invention of the double horn. The illustration that accompanied Eichborn's article (below) matches the layout of this horn exactly except for the extra loop in the the F-extension. In particular, the lower leg of the third valve B♭side is oddly not parallel with the other valve legs, as can be seen in the above photos and the drawing below.

This was the first double horn that Anton Horner used. In a letter to Osbourne McConathy dated July 3, 1956, he mentions that following the tour in 1900 with the John Philip Sousa Band in 1900 he visited Kruspe in Erfurt. "After the Sousa tour was over, I stayed in Europe for a month to visit relatives in Vienna and Bohemia, and my teacher, [Friedrich] Gumpert, in Leipzig. He was delighted to see me, and when I told him that I was playing one of his nephew's inventions, he told me that he had retired two years before....Then I went to Erfurt to see the man who who made my double horn. Krüspe had heard of Schmidt's new patent [sic, no Schmidt patent has been found], and since his two valve affair was rather temperamental in operation, he got busy and invented the valve [D.R.G.M. 182 267 (1902)] that is on his horn today - with minor changes [D.R.G.M. 232 038 (1904)]."

It must be pointed out that both Anthony Baines (1976, p. 224) and Herbert Heyde (1987, p.182) incorrectly state that this was a compensating horn. Neither gives a citation for this statement. Dr. Heyde compounds the error even further by stating that the unsigned example in the Deutsches Museum in Munich (Nr. 15265) and the article by Hermann Eichborn (ZfI, 1899, p. 981) actually pertain to the patent (DRP 117592) by Friedrich Butti from August 13, 1899. Inspection of the text of D.R.G.M. 84240 documents filed by Firma Ed. Kruspe, however, clearly shows that this was a full double horn (see below). Unfortunately this error has since been spread throughout subsequent publications, including the official catalog of the exhibition of Kruspe intruments at Erfurt in 2012, and, of course, throughout the Internet. No evidence has been found that there was ever a compensating double horn in the modern sense prior to 1906 when the instruments by Gebr. Alexander (Model 102) and Ed. Kruspe (Gumpert-Kruspe, D.R.G.M. 295 125) were introduced.

This model was copied by Robert Piering of Adorf with a more sophisticated thumb lever linkage than the simple tab attached to the connecting rod found here. On the Piering double horn the thumb linkage consists of a pivoted lever placed next to the upper rotor in the same manner as the Kruspe Horner Model, with the connecting rod attached at the midpoint of its arc. Robert Piering flourished in Adorf, Saxony from 1882 to after 1937. No date has been found for his double horn.

D.R.G.M. 84240 dated November 13, 1897 describes the valve structure of the horn in general terms. Its title is “Metal-Blechblasininstrument mit Doppelzylindermechanik und gelenkig verbundenen Stellventilen neben den Doppelzugventilen” (sheet-metal wind instrument with double cylinder mechanics and articulated connected control valves beside the double course valves). The protected innovations were the double-decker valves necessary for two sets of valve slides, and the tandem pair of rotors used as a change mechanism for F to  B♭ (see diagram Fig. 2 below and the page for D.R.G.M. 84240 for a full analysis).  It was announced  a few weeks later in Zeitschrift für Instrumentenbau:

The distinctive valve levers of this horn (below, and shown in Fig. 1 above) match those of a Kruspe single F horn and other Kruspe instruments from about the same period.  Engraved valve caps are less common on Kruspe horns but are occasionally found as on another single F horn ³ from their short-lived Leipzig branch circa 1893. The elegantly shaped linkage arms (lower photo) are typical Kruspe. The presence of a thumb rest is clear evidence that the bell is not original to this horn (see text, below). The bell is probably a transplant from a single horn since a thumb rest serves no purpose on a double horn and only gets in the way of the change valve lever.

The valve section is numbered "1" as shown on the casings of each the main valves (above). This is probably just a work number used by the maker to keep the parts of the valves together during assembly, but it is tempting to assume that this is the first valve section of this type. Details of this horn match those of a Kruspe single F horn from about the same period,  The brace between the valve section and tuning slide (above) and the small braces between the valve tuning slide casings (right) are typical of Kruspe and match the referenced Kruspe single horn.