G'day, it is a Maundy penny, the smallest silver coin minted in Britain.
Copper coins had been in use for quite a while by 1779, but the Maundy sets were still produced in silver, upto the present time.
The Maundy coins come in 4 denominations, 1d, 2d, 3d, & 4d.
They have a very simple reverse, but the really early ones (Chas II & Jas II) have some interesting flourishes.
Regarding the quality of the engraving & strength of strike: these were low volume products, and were produced before The Great Recoinage of 1816, when steam presses were introduced. As such, the "quality contral" was a lot different to what we are used to now.
A bit of history: look at the legend on the reverse. It's abbreviated Latin, "Mag Bri Fr et Hib Rex"
= "Great Britain, France, and Ireland, King [of]"
The British continued to claim the French throne for a few decades after that. The larger coins of that era have even more titles listed.
Peter in Oz
(who is chuffed that he just won a Maundy 4d of 1820 on
ebay)