Updated by J. A. Hefner.
The Sommerhoff signature is interesting: William A. [Albert?] Sommerhoff left Felgemaker with the Tellers brothers in 1906 to start the first Tellers organ firm. Sommerhoff left in 1918, then Albert Kent [superintendent of Felgemaker] joined, effectively bringing Felgemaker with him [somehow the company assets, contracts, etc. were absorbed by Tellers]. Sommerhoff's apparent work on this organ might show some sort of cooperation before 1918 [like Leblanc-Courtois-Holton brasses in the 1950s-60s before the 1961 decision to merge, then 1964 merger, or Elkhart instrument makers].
Identified through online information from Joseph Tuttle. -- The organ in St. Mary's in Sharpsburg is signed inside, "Albert Sommerhoff" and the year 1917. The original console was rebuilt by Organcraft in the early 1980s, and a new 8' Trumpet was installed in the Great, possibly replacing an existing rank.