UPDATE: The 2SK596S is discontinued from OnSemi.
I bought some 2SK596S-C low noise JFETs.
The device comes in a type SPA (SC-72) package similar to TO-92 (shown above on the right for comparison) and is otherwise notable for having very low Idss. It seems there were originally two versions of the 2SK596S (ranks A and B), but the latest datasheet implies that rank A has been dropped and rank C added and that the Vgs(off) range has been tightened. The three ranks are characterised by Idss range:
OnSemi are offering these devices as suitable for use in condenser microphones, audio equipment and telephone systems. The 2SK part number, the package type, and the FBET process suggests that this part comes from Sanyo technology (OnSemi bought Sanyo Semiconductor in 2011).