Has anyone seen these CG4A Glider images on snapshots

[Glider Pilot Daughter]

My Dad took hundreds of photos while serving as a Glider Pilot in WW2. On some of these photos have this little image of a CG4A glider printed on them. It appears to me that he must have made a mask with this image while printing the photo. I know he knew how to develop and print photos because in the 1950's he borrowed darkroom equipment and taught me how. Some of them seem to be upside-down or misaligned. Also I found negatives stored in a Kodak photograph paper box with a expiration date of 1945.

 

Has anyone seen this image on photo's? It would be interesting to see if these were shared or done by others.