Texas Instruments

• first lcd and slimline lcd

Model: TI-53
Battery: 2 x LR44
Adapter: 
Year: 1982
Chip:  TPO323
Info:  first LCD and slimline LCD

• slanted LCD
• RCI

Model: TI-53 slanted
Battery: 2 x LR44
Adapter: 
Year: 1985 ( RCI 17 85 )
Chip:  TPO323
Info: Calculator donated by Ludovisi Giancarlo in 2023 during the 2nd edition "the story with Texas Instruments" in Rieti, (World Chili Pepper Fair).

• slanted LCD

Model: TI-54
Battery: 2 x LR44
Adapter: 
Year: 1982
Chip:  CD4555,CD4551  
Info:  slanted LCD  generation

• majestic line

Model: TI-55
Battery: BP 7
Adapter: AC9132
Year: 1979
Chip: TMC1503          
Info: TI-55 same as TI-51 III, but TI-55 was sold in the US while TI-51 III was sold in Europe.

• slanted LCD

Model: TI-55 II
Battery: 2 x LR44
Adapter: 
Year: 1981
Chip:  CD4555,CD4556
Info:  slanted LCD  generation