Texas Instruments TI-38 Scientific Electronic Calculator (c.1980).
The TI-38 was a simpler version of the TI-35 introduced in the same year. Instead of the statistical functions of the TI-35 two conversion functions were added: DD<->DMS (Decimal Degrees to Decimal/Minutes/Seconds) and P<->R (Polar to Rectangular coordinates). The goal was to replace the TI-30 but market acceptance kept low. (Ref: http://datamath.org/Sci/Slimline/TI-38.htm.)