The tour is typically 3years in a unit but can be shorter or longer. First Sergeants can aslo move to another unit and pull atour there.
The First Sergeant, or Top, is the senior NCO of the Company, Battery, or Troop.
If the recruiter is an active duty US Marine he can become any grade that he earns through hard work, recommendations from a commanding officer and length of service time. Marines start as private, pfc, lance corporal, corporal, sergeant, staff sergeant and then gunnery sergeant. And finally the highest ranks of enlisted men the Master Sergeant and First Sergeant
You get staff sergeant I but after staff sergeant II and III you get staff sergeant first class. hope this helped ;)
When a First Sergeant leaves, it'll either be because they've been relieved of duty, or are about to be promoted to Sergeant Major. Who replaces the First Sergeant depends on the availability. It may be a Master Sergeant transferred from a staff position, or it may be a Sergeant First Class who is about to be promoted to E-8. You won't find Master Sergeants in line companies - Master Sergeants are found in staff positions.
length of duty
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.
A platoon sergeant is someone who is responsible for the care and well-being of a platoon of soldiers. It is a description of a job. A Sergeant First Class is a pay grade (rank). It is also called E-7, and abbreviated SFC. Usually (but not always) the job of platoon sergeant is given to a soldier in the pay grade of Sergeant First Class, due to their experience and skill. It is possible to have a well-performing soldier of the previous rank (Staff Sergeant) doing the job of platoon sergeant, and it is also possible that a Sergeant First Class could be doing something other than leading a platoon (staff duty, for example).
this position does not exist
YES
First sergeant
First Sergeant (E8).
The lozenge is simply a device to differentiate a First Sergeant from a Master Sergeant, Sergeant Major, etc.