I normally don't like to post names on the forum, but in this instance I will make an exception.
I recently got the following enlisted observer's uniform from a good friend, I mostly bought it to get the incredible French-made Observer wing:
When I bought it, the uniform came attributed to a R. Yates, with a hand-written card describing Yates. Unfortunately, I have not been able to even remotely verify that there was an R. Yates in the Air Service or Signal Corps that fits the specifics of this uniform.
For one thing, the rank on the uniform is for an Electrician First Class. Neither the Air Service, nor the Signal Corps seems to have used this chevron:
Electrician First Class seems to have been a Coast Artillery rank. The equivalent Air Service and Signal Corps grades were Sergeant First Class (three chevrons and a rocker). I know there was a shortage of enlisted personnel in the expanding Air Service and many men from other branches were transferred in--I have a grouping from a Navy Cook who was transferred to the Air Service. The Air Service did have Master Signal Electricians, but that was a grade higher than Sergeant First Class...