Here's Part 1 of a 5 part series.
This deckungswinkelmesser (deckungs = cover, winkel = angle, messer = measurer) is an odd variation that I've only ever seen one of (and this is it). The gauge inside is calibrated in degrees (instead of mils), and percent. The body and outer frame of the deckungswinkelmesser appear to be made of brass, except for the pivot and loop screws, which are steel. The directions plate in this case is made of brass, but some are aluminum. The white on the reverse side is an early type of plastic, which typically shrinks from age, and cracks at the screw (or rivet) corners due to the strain. An oddity which I suspect was used as a form of identification for a deckungswinkelmesser which shows degrees and percent, is that the protective bulge where the lens is mounted is flat instead of curved, as is the matching part of the folding framework. This being flat instead of round is unique to this deckungswinkelmesser, as all the others I've seen had a rounded bulge. The gauge itself reads from 49+ to 19- degrees, and 90% up, to 30% down. I have no idea what the special purpose for this particular deckungswinkelmesser is. Those for the MG34 and MG42 are marked in mils, which corresponds to the calibration of the searching fire device to control elevation.
The deckungswinkelmessers were used by the lafette-equipped MG crews for measuring the relative elevation of an obstruction (cover) to be shot over. This could be a tree line, a building, hillside, or other troops. This measurement could then be dialed into the lafette (could be an artillery lafette, MG lafette, or other, depending on use), and then the projectile (bullet, artillery projectile, etc.) would not hit what you didn't want it to hit. It can also determine, in this case, degrees of elevation (or depression) of a road, river, hill, etc., for a variety of calculations. Most deckungswinkelmessers are calibrated in mils only. They fold as shown in the picture to conserve space in the MG belt pouch.
The loop on the top often had a string or shoe lace tied to it to help prevent dropping. The loop is hinged, and when the deckungswinkelmesser is held by the loop, the deckungswinkelmesser hangs exactly vertical due to gravity. This provides a very accurate reading of a different elevation, since the gauge is certain to be vertical when reading it.
Length when open is 6" (about 15 cm) without the loop. Closed it is about 4-1/4" (10.5 cm). Width, not including the bulged area, is about 1" (2.5 cm).
The manufacturer for this device is Möller / Wedel with the serial number No 13149 Most if not all of the deckungswinkelmessers are stamped with the manufacturer, scale, and number.
The directions read:
"Hold kneeling (to put it at about the same height as the MG on the lafette) in front of one eye, so that the cover and graduation lines can be read at the same time. Read the graduated line number. Mil spacing is 5/64000", which is interesting, because the gauge is calibrated in degrees and percent.
You don't actually look through the deckungswinkelmesser lens (the bulge on the side of the main body). You hold it in front of your eye, just far enough away to be able to see through AND around the lens, and you visually compare the elevation of the obstacle to the lines on the gauge. The white plastic plate is used to write down the number using a pencil, which can easily be erased with a wet thumb after use.
Over the next few days, I'll post pictures of 4 other types of deckungswinkelmessers in my collection.
Click on the picture to enlarge it.