A little about the frames and process:
I have modern Morso Gullotines and AlphaMaccine underpinners which are both Italian made (of course!). The vertical edges are finished with glue and pins to ensure they will never separate.
A 6mm gap is left between the edge of the canvas, and the frame creating a shadow, giving the illusion of the painting "Floating" in the frame. This also allows some of the edge finishing of the painting to be visible. I ALWAYS finish my edges to match the face of the painting.
With all things wood related (Being a natural product) it needs sanding and finishing. My natural frames are finished with a Gillys Liquid Beeswax to give a classic lustre and finish, and colours are sprayed with a varnish finish.
Many framers and artists tend to offer a Gesso (Plastic) finish for colours and sometimes even natural. I will only ever use wood. It looks better, finishes better and should anything ever go wrong with a bump, or if you are moving your art, it can be sanded and finished again. Once gesso if scratched or marked, its virtually impossible to restore.