Is there any interesting content in the letters? Likely not very interesting due to censorship, but perhaps somewhat interesting? Also, the photos are a bit blurry on my computer screen - do the return addresses give any clues as to which ship or which base the person was based at?
Also, the covers and stationery appear to be privately produced - the kind that was being sold in base PXs and shops around military bases. Official stationery would have the penalty indicia on the envelope and not have required any postage where this person has placed postage.
Here is an example of what Navy stationery looks like - this is a cover that was mailed during WW 2.
