The is a thin-type, hybrid IC designed for use in stereo audio amplifiers (AF power amplifiers). It belongs to the STK410-XXX series and is commonly used in mid-range home stereo systems, active speakers, and mini-component amplifiers.
A full technical breakdown, including pinout and electrical characteristics, is available via the STK411-210E Sanyo Datasheet (Scribd) . stk411-210e circuit diagram