There are a bunch of these types of wappen that are for police and/or fireman outfits. This picture comes from the 1932 Junkers catalog and is one of the most common I have seen. Sorry not military.
This is my Rheinland (fire?) helmet that I purchased years ago from a fellow Harley rider. Same eagle without imperial trappings and Rheinland crest.
It came with the carrying case, missing the straps, but I thought it was pretty cool. Also, it's my only 'kofferhelm', as described in Joe's reproduction of the Junker catalog. Notice that the eagle's feathers are different under the crest as well.