I don't collect calculators but I often have opportunity to grab one or two with some electronic junk. From simple abacus, through slide rules and mechanical stepper drum machines, to electronic units, sometimes even programmable.
First wide-spread calculators were abacus calculators, a typical with round pieces of wood on steel rods in wooden frame. Abaci are used even today, especially in small shops in Ukraine or Lithuania, and calculating on them can be really fast if it's done by experienced person.
In engineering, slide rules were popular calculators. Contrary to abacus, slide rule allows to divide and multiply numbers, but it can be used to compute logarithms, powers, roots and some trigonometric functions. The set of logarithmic scales on sliding parts made the most time-consuming computations easier. Slide rules were made of different materials, in different sizes (from full-sized ones to pocket-size units) and in different shapes (linear, circular, even with replaceable nomograms). There were also specialised rules to convert units or compute values (in ballistics, airplane navigation, architecture, cryptography etc).
Simultaneously more expensive mechanical machines were made. Mechanical arithmometers could be used to perform all 4 operations using counters. Arithmometers with pinwheel - gear with different count of protrusions, were manufactured till mid-80s. Abaci and mechanical arithmometers are used even today, especially in former Soviet Union countries. Why? Because they don't need electricity.
Since late 70s electronic calculators became cheaper and more accessible. They became smaller too, from large, tabletop units to pocket, microprocessor-based battery-powered calculators known today. Nixie tubes became replaced with VFD displays, VFD with LEDs, then LCD. Some really old units had CRT display, but they were so expensive that they never gained popularity. First calculators were transistor-based, sometimes even had ferrite memory. Later units were made of TTL chips, later were one-chip constructions with dedicated chips.

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Purely analog mechanical:
Name Type Year
Slide rules Mechanical 1920s-1970s


Mechanical (discrete):
Name Type Year
Abacus Simple mechanical 1950s?
Triumphator Mechanical (pinwheel, sliding) 1960s
 Счетмаш  Феликс (Schyotmash Feliks) Mechanical (pinwheel, sliding) early 1960s
Счетмаш ВК-1 Тип ВДР (Schyotmash WK1) Mechanical (pinwheel, keys) 1960s
Predom Mesko KR-13 Mechanical (pinwheel, keys) 1970s


Electronic (portable and tabletop):
Name Type, Display Year
Elwro 105LN Desktop simple, VFD 1970s
Elwro 131 Desktop simple, VFD 1980s
Elwro 143 Desktop Simple, VFD 1970s-80s
Elwro 144 Desktop Simple, VFD 1980s
Elwro 182 Desktop Scientific, VFD 1980s
Brda 10U Pocket simple, LED 1980s
Brda 11U Pocket simple, LED 1980s
Brda 12U Pocket simple, LED 1980s
Commodore SR-36 Pocket scientific, LED 1970s
BMS800J Pocket simple, VFD 1980s
Lloyd's Accumatic 311 Pocket simple, VFD 1970s
Elektronika MK-60 (Элэктроника МК-60) Pocket simple, LCD 1980s

Power supply for Unitra portable calculators

      List of most Elwro 1xx-line desktop calculators