Scott's does say that excellent forgeries exit. I'm no expert, by any means, but comparing your stamps overprint to the example given in the catalogue I can see at least three areas of possible discrepancy.
1. the wing of the plane on yours extends too far over the tail. On the original they are almost even.
2. the accent over the e on yours is merely a dot, whereas the original seems to show an accent aigu (or acute - a right leaning accent).
3. the lower case I extends right down to the base line, but yours is short.
These are just some observations, but I'd lean toward counterfeit.
edit - now seeing them side by side, I think there are other obvious differences. The shape of the left wing itself, and the overall shape of the tail.
I realize the image in the catalogue is probably not perfect, but that's all I've got to go on.
I'm sure others will chime in.