Lovely Ladies Vest Approx Size 10

When I bought this I saw the Lands End tag.. and didn't realize that it was on the hanger. There are NO tags anywhere inside this vest. I'm a 12, I put it on, and it fits at the arms, nothing is too tight until I go to button it up. I can't get it buttoned but one sneeze might blow the buttons OFF! My guess is that it's a 10. It is 40" from button to button around the tummy! It also appears not to have been worn before. As you can see from the pictures the fabric has a satiny sheen