Never seen anything like that. My immediate thought is rack number, but that wouldn’t necessarily make sense. Great set. Would also be neat if you could ID it.

You're welcome Mark, or is it "Mark 40"?  Just kidding...Have a good one!

WW1 brass cased marching compass inscribed F-L No.159112 1918 with leather carrying case. I'm can't make out the lettering on the top side of the compass, but again mine has a wonderful rich patina but I like it.              

Thank you @atb   I forgot to mention that it is larger than usual sized unit insignias. (CIB for reference)  

Thanks aznation for the links. Quite a pile of information. I learned something so it’s a good day  mark

U.S.E.D. CREAGH-OSBORNE MARCHING COMPASS MARK VII MOD. E SPERRY GYROSCOPE CO. BROOKLYN, N.Y.   https://americanhistory.si.edu/collections/object/nmah_1465344#:~:text=Description:,the Sperry Corporation in 1933. Description Frank Osborne Creagh-Osborne (1867-1943), Superintendent of Compasses in the Royal Navy, introduced this type of instrument in 1917. The bottom of this example is marked "U.S.E.D. CREAGH-OSBORNE MARCHING COMPASS MARK VII MOD. E SPERRY GYROSCOPE CO. BROOKLYN, N.Y." Here, “U.S.E.D.” stands for United States Engineer Department (aka Army Corps of Engineers). The Sperry Gyroscope Company was established by Elmer Ambrose Sperry in 1910 and became the Sperry Corporation in 1933. Ref: E.A.R., “The Creagh-Osborne Compass,” The Geographical Journal 49 (1917): 63-65.   The one below is mine but let's just say it has some patina.      

Great photos!!! Nice photo there of Jack Chennault who would command the "Aleutian Tigers" during his time in the Alaskan Theater. There's a great book on the 11th by John Cloe aptly called "The Aleutian Warriors." These pilots were tough as nails to be flying in the Alaskan weather (williwaws and all).

Thanks for sharing, nice photos.

104th Field Artillery. It appears to be an unfinished cloth version of the unit's Distinctive a Unit Insignia. 

Based upon burial….another unit…… “L” company  19th engineer    Question:  Any markings on lining or pockets, etc?