Those are great pictures and yes, it certainly looks like a river pearl just by it's colors, shape and surface. Natural freshwater pearls, especially mature ones have a degree of calcite distributed through the structure, so with that it's difficult to get the depth of the views we see from natural saltwater pearls. That said, those are points to support natural origin. This pearl has a nice glow to it.
The last image has an inclusion of conchiolin and although the prongs obscure it somewhat, it appears to be present in several layers. Also a point in favor of natural.
I'm glad we revisited that one.
G7 has similar color, but the ring and margin contrasts near the hole have me skeptical of natural origin. I'm inclined to think it's an early culture period.
How old does jewelry need to be antique as opposed to vintage? 100 years? If that's the case, we'll be adding the term to cultured pearls in the foreseeable future.