During the evolution of Casio calculators there were many different types of display.
I will try to put a timeline in Casio's concept of the calculator display's.
(This will not include other brands displays and only what Casio used)
Illuminating pad (1954-1959)
Nixie Tubes /cold-cathode display tube
amber gas-discharge individual display
amber gas-discharge single segment display (Casio 101-L)
VFD /Vacuum fluorescent displays
First generation vacuum fluorescent display (VFD) using a separate tube for each digit.
Second generation vacuum fluorescent display with all the digits in a single round tube.
Fourth generation vacuum fluorescent display in a flattened package made by welding a domed piece of glass onto a flat piece
Liquid Crystal Displays (first generation)
Liquid Crystal Displays (Second generation) with black digits and a yellow background
Liquid Crystal Displays (Third Generation)
Colour Liquid Crystal Displays