Here are some photos of a recent piece that I picked up at the MAX show last year. While it is an officer piece of high gilt and silver flash, officer 1892 devices were cut from the exact same dies as enlisted insignia.
Hopefully, you can see the slight "curve" I refer to, especially in the southern latitudes. They are slightly angled to conform to the curvature of the globe. I cant be exactly sure, but it looks like your two pieces have this, which from my decades of study, is correct for period pieces. Reproductions have latitudes that are perfectly straight across the globe, as if someone was evenly cutting a piece of cake, the lines are perfectly symmetric and parallel.
Again, I cant explain the beak not being cutout on the bronze piece. But I surmise that given that this is a "harder" material that wont bend, as you said, the die may not have been able to cut the normal depth. Lastly, sense it is made for a saddle cloth, less snags could have been built into the die design (even though it is highly unlikely a manufacturer would recut new dies for this small point). I also surmise that these saw very limited use, given the fact that yours shows a wingtip missing (most likely snagged and broken), these are rarely seen, and the Corps eventually went to leather insignia, supports this summation.
Thanks for posting, this thread opens a new chapter on an insignia that is one of my personal favorites and one that few people have any expertise due to the age and scarcity.