I got these recently, and they finally came today.
I think they're unissued France Parcel Post stamps from 1938, as I couldn't find a Scott# for them in these colors. My 2012 Scott C-F catalogue seems to have a footnote under Q145 that says "Two additional values, a 10c rose lilac and a 15c ultramarine were prepared with this set but not issued. Values, each stamp: $90, never hinged $150. Both stamps also exist imperf. Values, each $82.50; never hinged $150."
Do my stamps seem to be these unissued stamps? Both the 15c ones look the same blue color (I guess ultramarine). The 10 ones seem to have a slightly different color though. The perforate one seems like rose lilac, but the imperf one looks more pink. All stamps look MNH, though they do seem to have some slight bends. They all also seem to have mark on the back in approximately the same location. Is this a stamp expertizing mark? If so, which is it?
I don't have a more recent France catalogue, or a more specialized one. Are those values still valid?