This may have changed, however when I served....
E1 to E2 was six months time in service.
E2 to E3 was one year time is service, six months time in grade.
E3 to E4/SP4 was eighteen months time is service, six months time in grade, and recommendation of an E5 or higher.
So no less than eighteen months, provided you earn good reviews and have no disciplinary action.
Specialist is a rank - Pay Grade E-4 - which is classed as lower enlisted. Pay is equal to that of a Corporal, but Corporal is the higher rank of the two (Corporal is a noncommissioned officer rank, Specialist is not).
There is no Specialist Eighth Class in the US Army or Marines. Most specialist ranks were phased out in the 1980's. Specialist Fourth Class (Spec 4), paygrade E-4 is still awarded in the US Army for some MOS's.
In the US Army, there's two ranks - Specialist, and Corporal. In the US Marines, it's just Corporal. The Specialist rank in the Army is not an NCO rank, whereas Corporal is.
March of 1955.
T.Sgt is the abbreviation for the current Air Force Rank. SGT (T) was the abbreviation for the Army rank with later gave way to the various Specialist ranks,, which were then reduced to only one Specialist rank.
Specialist 5 - it's a discontinued Army rank. A Specialist got the same pay as a Sergeant (also pay grade E5), but was not a noncommissioned officer.
Neither. A Tech 5 was equivalent in pay to a Sergeant, but did not have a Sergeant's authority. The rank was done away with when it was replaced by the Specialist ranks, and there is currently no Tech 5/ Spec 5 rank - all Specialist ranks except for Specialist 4 have been done away with.
THE QUICK MARKETING
SPC is the abbreviation for Specialist. Currently, there is only one grade of Specialist - E4. Specialist grades used to go all the way up to E9 (although the Specialist 9 or SP9 was only theoretical - nobody had ever actually been awarded that rank). At that time, the E4 Specialist was abbreviated as SP4. However, all the Specialist grades above E4 have since been done away with, so there was no need to indicate the pay grade with the rank, thus the abbreviation became SPC.
No
Yes, that is the proper spelling of "specialist" (one with special training, or a rank in the US Armed Forces).
Just "Specialist".