The 7th Army is the highest level, then works it's way down from there.
WWII hierarchy works as such:
ARMY OR CORPS
DIVISION/BRIGADE
REGIMENT
BATTALLION
COMPANY
PLATOON
The above is standard, except for bastard engineer units, such as the 540th Engineer Combat Regiment, who went where needed and were NOT in a division.
In the case of those units, they were also under control of an ARMY GROUP or CORPS.
For instance, my father unit's during various times of the war were:
5th Army, 7th Army or VI Corps
The 106th came into the Battle of the Bulge under First Army. I am doing more research to see if and when they were under 7th Army control later in the war. If not, then this explains the 7th Army insignia and maybe he was sent to another unit, an engineering unit. Stand by. Just woke up a bit ago and having first cup of coffee of the morning.
Proud Daughter of Walter (Monday) Poniedzialek
540th Engineer Combat Regiment, 2833rd Bn, H&S Co, 4th Platoon
There's "No Bridge Too Far"