Not sure about the Army but in the Marine Corps, a “toilet seat” was the badge you got for being a Marksman. There are three levels of qualification : Marksman, Sharpshooter and Expert. The Marksman badge is square with concentric circles like a target. Or, as we call it, also resembling a toilet seat.
I never heard it called that in the Army but we certainly did in the Marine Corps.
That’s what I thought. Thanks.