To me they just look like regular first-harvest tissue nucleated FWP.
The FW pearls often referred to as keshi are 2nd harvest pearls. That is, after they take out the first-harvest pearl, they place the mussel back in the water, and a new pearl forms in the existing pearl sac. Their shapes tend to be more irregular as a result. Sometimes a form is inserted so that the keshi will take on that shape. This is how one gets coin pearls, pearls shaped like stars or crosses etc.