Well...every other rank that isn't First Sergeant, I'm guessing...
First Sergeant (E8).
YES
There is no such rank as "First Class Sergeant". You have either Sergeant First Class, which is E7, or First Sergeant, which, along with Master Sergeant, is E8.
Gunnery Sergeant is pay grade E7, and the equivalent Army rank is Sergeant First Class.
The lozenge is simply a device to differentiate a First Sergeant from a Master Sergeant, Sergeant Major, etc.
Master Sergeant in the Army is pay grade E8. First Sergeant is the other Army E8 rank.
I assume you are talking about E-8 and E-9 ranks. At E-8 you become either a First Sergeant or a Master Sergeant. If you take the First Sergeant route the next rank becomes Sergeant Major. If you take the Master Sergeant route the next rank becomes Master Gunnery Sergeant.
Sergeant is the higher rank.
In the Army and Marines, it's First Sergeant, which are both pay grade E8. In the Air Force, Master Sergeant is pay grade E7, but First Sergeant isn't a separate rank, although it is denoted with a diamond similar to what it used on Army and Marine Corps First Sergeant rank insignia. In the Air Force, the designated First Sergeant can be pay grades E7 through E9.
In the Army and Marines, it's First Sergeant, which are both pay grade E8. In the Air Force, Master Sergeant is pay grade E7, but First Sergeant isn't a separate rank, although it is denoted with a diamond similar to what it used on Army and Marine Corps First Sergeant rank insignia. In the Air Force, the designated First Sergeant can be pay grades E7 through E9.
In the United States Army, the rank of First Sergeant (abbreviated as 1SG) is above Sergeant First Class, below the ranks of Sergeants Major and shares the paygrade of E-8 with Master Sergeant. The rank of First Sergeant carries more responsibility than the rank of Master Sergeant, and the rank may be either given to the soldier upon promotion to the paygrade of E-8 or they may be "laterally promoted" (promoted in rank but not paygrade) from Master Sergeant at a later date. They are also known unofficially as Top Sergeant or just Top, due to the fact that First Sergeants are the most senior non-commissioned officers in an Army company. Right - that is Current, but what was the difference during World War II, when Master Sergeant was technically higher than First Sergeant (Although both E-7)? - Master Sergeants were higher in responsibility than FSgt's. Master Sergeants were commonly Battalion level NCO's during WWII, also more experienced members of the Armored and Air Corps. First Sergeant was the most senior NCO positions in a Company.
The Army and Marines both have two ranks in the E8 pay grade - Master Sergeant, and First Sergeant. There is one E8 rank in the Air Force - Chief Master Sergeant. If they hold the position of First Sergeant, they get a diamond on their rank insignia to denote it, but their rank remains Chief Master Sergeant.