Question On C23 Ffc Experimental Nitro W VA 1939

Scott stamp# C23.
First Flight cover via Experimental AM-1002
Nitro, West Virginia-Marietta, Ohio.
Mailed from Nitro, West Virginia. May 12, 1939
no cancel on back of envelope.

I have Questions about this cover??
Why was there no Marietta, Ohio backstamp??
Does No backstamp means it isnt a experimental cover??
value of cover??
I have other covers that are the same way from different towns.

Another, very nice cover.
Things to look at, first the year, 1939, most true experimental are prior to 1930.
Next the cities of Nitro, WV & Marietta, OH are less then 100 miles apart.
Was there a real need for air mail? Maybe!
By 1939, once a stamp was cancelled at a USPO there was no need to cancel again.
At best this was the first time airmail left directly from Nitro.
It is likely a manufactured event to mimic the experimental flights of a decade or more before!
With a little more research we would likely find out that Clement Glowienka was a collector who likely answer an ad to be a recipient of this special event. Since the return address is not a business or person but the flight itself.