Found these and some flat buttons at an old mill house from the latter part of the 18th century. Strangely, the old coin I found was a 1918 wheatback. Some buckles and a broken copper measuring gauge. Any help on ID's appreciated!
I don't know that it'll work after olive oil. Please read my post in the cleaning and preservation section of the forum. It is titled "How to Clean Buttons."
I don't use olive oil in general, but it's very bad for pewter, since it can make the compromised metal even more soft. I seal my pewters with elmers glue mixed with a few drops of water and painted on the button.
clear urethane works well too, and that might have to be what you'd use, since Elmers is out now that oil has been applied.
And for those who don't think it's worth sealing buttons like this, think again. First, we have a Duty to preserve and care for what we find. Second, it's good practice for when you dig a Valuable pewter button like an interlocking "USA" or similar.