Boots 224 Memory

3v (2x AA batteries).

Display is 8 digits, green fluorescent.

4-function, %, square root, memory.

Integrated circuit - NEC D1877C.

77 x 135 x 18 mm (3.25" x 5.7" x 0.9").

Made in Japan.

This is a Casio H-1 re-badged for Boots.

There is also a second version of the 224 Memory which is slightly different.

Boots 424 SCIENTIFIC

3v (2x AA batteries).

Display is 8 digits, green fluorescent.

Scientific.

Integrated circuit - NEC uPD574C.

83 x 144 x 22 mm (3.25" x 5.7" x 0.9").

About 1976.

Made in Japan.

Is a re-badged Casio fx21.

Boots 425 SCIENTIFIC

3v (2x AA batteries).

Display is 8 digits, green fluorescent.

Scientific.

Integrated circuit - NEC uPD574C.

83 x 144 x 22 mm (3.25" x 5.7" x 0.9").

Made in Japan.

Is a re-badged Casio fx31.

Boots PD-525

7.5v (5x AA batteries).

Display is 8 digits, green fluorescent, and thermal printer.

4-function, %, memory.

101 x 189 x 47mm / 4x7.5x1.9"

Made in Taiwan.

Boots 527

Display is 8 digits, LCD.

Scientific functions.

This model with its LCD display is an immediate follow-on from the VFD (Vacuum-Fluorescent Display) calculators above, as the technology developed.
Apparently also manufactured by Casio for Boots in the late-1970s/early-1980s time period.

British calculators