Thank you for your answer and your research.
Firstly, I didn't think it was a copy because I assumed that a copy would have been made according to a known design and it would have poor details at the back.
I agree some details are unusual, if you're right it would be disappointing but that was the risk
I wasn't worried about it because the badge has a few features that I liked :
- a curved shape like a badge which was worn a long time on a cap (maybe not easy to see in the picture).
- the material looks fine and is quite "heavy"
- the lugs and welds look good, like those found on original badges.