This is one of the military sights produced by Wild Heerbrugg. In this case the top half (the optics) are Wild Heerbrugg where the bottom half (the adjustment part) was made by another Swiss company called 'Bachmann & Co' from Glattbrugg in the Zurich canton. It was immediately clear that this instrument came from some military gun. However, the search for which gun that was took some time. After much trial and error I have narrowed the origin to one of two guns:

• 9 cm Panzer abwehrkanone from 1957

• 9 cm Panzer abwehrkanone from 1951

While looking at the pictures from the Swiss museum on military vehicles this instrument can be seen to the left of the gun (when looking from behind the gun). Based on the dating of the two parts (Wild: 1954, Bachmann: 1958) it is most probably from the 1957 version although it can also have been possible they were used for both. The guns themselves were specifically made for the Swiss army, how one of these sights ended up in the UK is not clear but as it was part of a larger set of similar devices it probably came from (another) collector. Unfortunately requests to the Swiss museum have so far not resulted in additional information.

The sight itself is build very sturdy (probably to withstand the firing of the canon) and uses a bayonet coupling to the gun. Once put on the gun the device can be levelled with the aid of two small leveling vials and the two unmarked circular knobs. Once levelled the device probably looked in the same direction (with the dials set to 0) as the gun. Using the large rotary dial the instrument can be rotated horizontally. Using the knob on the back of the instrument it can be rotated vertically for elevation changes. Distance can be read through the optics which have a distance scale (probably based on the 'average' length of a tank). The top (Wild) part can be detached from the bottom (Bachmann) part so different 'marriages' of serials can be created.