Texas Instruments
Model: SR-51 II
Battery: BP 6
Adapter: AC9131
Year: 1977
Chip: TMC0501 / 581
Manual: with permission www.datamath.org
Info: MAJESTIC line
Model: SR-52
Battery: 3 x AA
Adapter: AC9130A or DC9105
Year: 1975
Chip: TMC0501 / 0524 /0595 / 2xTMC0599, 2xTMC0561/0562
Manual: with permission www.datamath.org basic library
Info: classic second GENERATION