Hi Jeremy,
I have called my friends and he has contact with the farmer.
The pearls in drop form in the picture is bead-nucleated, but the nuclei are round, not drop form.
Here are some pearls, whose are bead -nucleated and the nuclei are button form. The pearls were brought for the last fair and have a size of ca. 11x13 mm. At first look, they are similar to normal barock pearls. The price is also reasonable (I offer them with 30-35 Euro/piece). If one look them carefully, something is different. I tried to cut them into two parts. But it is easier to cut the finger than the pearls. I had to give up after 15 minute test and used brutal force to remove the shell.
The nuclei are about 8,8-9,2 mm. The shell is 1mm thick.