August Clemens Glier (1846-1897) was the third generation in his family of musical instrument makers and dealers. The original company was founded in the early nineteenth century by his grandfather, Christian Wilhelm August Glier (1793-1825) and continued by his father Wilhelm August Glier (1821-1876). August Clemens founded his own company as a string instrument maker and trading company in Markneukirchen in 1878. By the turn of the century it became a very well-known company trading both within Germany and worldwide. It marketed instruments, parts and accessories by smaller manufacturers. After the death of August Clemens his sons Otto Clemens Glier (1879-1914) and Albert Paul Glier (1882-1977) took over the company with Paul continuing as sole owner following Otto's death. The company was discontinued in 1961.

A.C. Glier also marketed a broad variety of instruments including  brasses, woodwinds, and strings, and also zithers and the  bandoneón a type of concertina very popular  Argentina.  In 1911 Glier provided the first 18 insturments for the newly founded Posaunenchor of the YMCA at  Niederndorf.  The present “first class soloist horn” was ordered by Pastor Müller in care of Prof. Ernst Klinger apparrently at the Evangelisch-Lutherischen Landeskirche Sachsens Posaunenmission in Grossenhain, Dresden, Germany (see its original invoice, below).. 
 

I don’t know who These Guys are but the horn player is holding a single Bb horn (left-handed) very similar horn to this right-handed one by August Clemens Glier. They are believed to be from eastern Europe or possibly Germany from circa 1925-30.