Bust of Isaac Newton by Roubiliac

I was not able to find this particular piece on the internet. I could not make out the last word on his back. It appears to be an older piece.
Louis-François Roubiliac (or Roubilliac, or Roubillac) (31 August 1702 – 11 January 1762) was a French sculptor who worked in England, one of the four most prominent sculptors in London working in the rococo style. He was described by Margaret Whinney as "probably the most accomplished sculptor ever to work in England"