Texas Instruments

• euro line

Model: TI-15 lcd
Battery: 2 x AA alkaline
Adapter: 
Year: 1982
Chip: Taiwan
Info

• euro line

Model: TI-15
Battery: 9 volt
Adapter: 
Year: 1981
Chip: TMC0981
Info: EURO line 

• overhead

Model: TI-15 overhead
Battery: 
Adapter: 
Year:  
Chip: made in China
Info:  The California based company Stokes Publishing Company, Inc. distributes under the label "The Educator®"
calculators optimized for teaching purposes. William T. Stokes filed already July 30, 1991 the US Patent Application U.S. Pat. No. 5,035,502
 with the title "Transparent calculator for overhead projection".

• LCD-1982-1987

Model: TI-18
Battery: 2 x LR43
Adapter: 
Year: 1983
Chip:  TPO311
Info:  modern LCD  1982 - 1987

• first lcd and slimline lcd

Model: TI-20
Battery: 2 x LR44
Adapter: 
Year: 1980
Chip:  TPO326
Info:  first LCD and slimline LCD