Strange female Marine chevrons

[SgtMaddoxUSMC]

Has anyone see these before or have any information?  The only ones I have seen are these three ranks, never seen a PFC or SSgt or above.  Would be from sometime 1960 or after, used til when?  Also curious to know which uniform this would have been worn on.  Hope someone has some info or other examples!

[SgtMaddoxUSMC]

Also should note the NMMC has an example that was donated in 1979 so would have been used sometime before then (and possibly after, as well) 

[Allan H.]

For some reason, I was thinking these were related to Junior Marines? Now they are called "Young Marines.

 

Allan

[SgtMaddoxUSMC]

Allen,

I don't believe so.  As far as I can tell these are regular female Marine regulation sized chevrons from either the 60s or 70s.  Could have maybe been an experimental thing possibly?
Very strange that in all my years I have only ever seen these three ranks.  Not like these three particular pieces but every time I have seen these in other collections or for sale and the only ranks that seem to be out there that I have seen anyway are LCpl, Cpl and Sgt.  I ASSUME there is at least a PFC version.