I want to give my daughter a shagreen box that I have had for years.

The box is French , 'D' shaped with a handpainted scene on the top and bottom.
I remember when we bought it that the dealer recommended that we oil the shagreen part every few years.

My husband knew what to use, he is gone now and I don't know what to use.
The box has a sterling edge top and bottom at the opening hinge with the body of the box being shagreen. The hand painted scene needs to be treated again with a note to my daughter for future reference.

Was it mineral oil that was used to highlight and preserve the shagreen?
Any help would be appreciated.