I picked these up in auction last month. A couple of small Spanish colonial coins from Lima - pictured below with a farthing to give an idea of the size.
I find very amusing that these little coins are tiny miniaturisations of the larger 8R with practically the same design and details - and even the elaborate edge detail that was done turning the coin between two parallel linear dies. Such an awful amount of work! As the mints were paid on the basis of weight of silver minted, there was little incentive to mint small coins and these are quite hard to find in good condition.
The vast majority of the silver mined in America at the time was used to mint 8-reales, often meant to be sent to Spain or for the trans-pacific trade. In particular and looking at these two little ones, in 1755 in Lima it was recorded 55,686 kilos of silver minted into coins, of which 53,111 were made into 8Rs and 4Rs and the rest (less than 5%) was left for smaller change - 2Rs, 1R, 1/2R