Arbroath Abbey gravestone

Visited Arbroath Abbey today, which is marketed as the "birthplace" of the Scottish nation because the Arbroath Declaration was written there in 1320. (In Scotland the Arbroath Declaration is treated with much the same reverence as Magna Carta in England.)

While we were there, I came across this intriguing gravestone. I don't know what to make if it. There seems to be an angel and also a woman using a pair of bellows on the sun.