Electrolux Corporation 1924-2002 & Aerus LLC 2003-present Model Identifications
Model Numbers—TANKS & UPRIGHTS
Roman Numerals 1924-1954
Single Letters—(tanks) 1954-1979 (E-Economy; T-Thrift; S-Special; *F-Fully Automatic; *R-Rudimentary; *G-Gentle; *GH-Gentle Hospital; *L-Limited (*conjecture)
4 Digits—1968-1994 (seems to be random as you mentioned); some with a letter suffix to indicate a modification
Alphanumeric—1994-present (Prefixes unique to each type of cleaner; suffixes reflect cosmetic &/or mechanical changes
Model Numbers—TRIPLE BRUSH CLEANERS
B-7—1959-1963 (single stem handle, hard-wired, reset button)
B-8—1963-1983 (double stem handle, removable cord (late were hard-wired); no reset button)
B-9—1983-1984 (new design with plastic base and hood)
B-10/1522—1984-1992 ('B-10' used in literature & on packaging; '1522' on nameplates—due to USA & Canadian contributors)
1732—1992-1993
1739—1993-1994
S105 with letter suffix for design—1994-c2006
S165 with letter suffix for design—c2006-present (no cord reel)
Model Names TANKS & UPRIGHTS—1974-present
It seems Consolidated Foods, which became the majority shareholder in 1968, chose to add model names. I saw literature advertising a contest to name the 1205, but apparently nothing came of it.
The 1974 '50th Jubilee' 1205 (nicknamed 'Golden J') was the first to have both number and name. The 'Super j' was a modification of the Jubilee cleaner (and looked quite similar) with a "super" more powerful motor, which necessitated the slight lengthening of the tank body.
'Olympia One' was the official 1980 Winter Olympics cleaner. The Canadian market sold the straight suction "Olympia II" for a short time,
'Diamond Jubilee' represented the company's 60th anniversary in 1984.
Other name choices have no significance to style or design until the 'Lux Classic' (2003-present)—referring to the Canadian design of 1982; 'Lux Legacy' (2003-present)—referring to the 1982 Canadian design with the onboard tool holder added in 1992.
Model Names—TRIPLE BRUSH CLEANERS 1965-present
Carpet Beautifier—1965-83 (originally it was the name of the optional shampooing component)
Floor Beautifier—1983-1988
Floor Pro—1988-1992
Floor Pro Epic Series—1992-1999
Floor Pro Encore—2000-2002
Lux Floor Pro—2003-present
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Electrolux Canada Model Identifications (credit to Doug Smith)
TANKS & TRIVACS
Roman Numerals 1931-1942 (Model XII import)
Double Digits with Z or ZB prefix 1934-1973 (beginning with Z24 English import)
Triple Digits with AP prefix (All Plastic, automatic) 1973-1982
AP—1973-1976 (All Plastic, non-automatic)
SAP—1979-1982 (Special All Plastic, non-automatic)
Quadruple Digits with E prefix (Electronic) 1982-85
Quadruple Digits 1985-87
Letter Prefixes 1934-1969—Z stands for 'integer', like the USA's # symbol: "N. Bourbaki", a group of mostly French mathematicians which began meeting in the 1930s, devised a thorough unified list of symbols for all mathematics. Z literally stands for Zahlen, the German term for number. The second letter indicated a modification of the original design. 'B' represented Canadian modifications.
E Suffix 1970-73—indicates the electric hose inlet added to the Model 89; so the model designation went from Z89 to 89E.
TRIPLE BRUSH CLEANERS
Double Letter with Digits (B for Buffer & 2nd letter for Canadian design) 1946-1966
B20-series 1964-1982 (20, 21, 22, 22J, 25, 28)
B50 1982-1985
2101 & 2101A 1985-1987 (sold also in the USA)
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European Model Identifications
TANKS & UPRIGHTS
Roman Numerals—1912-1933
Double Digits with Z or **Z_prefix—1933-1979
Triple Digits—1965-? (beginning with "Challenge" & "Trident" labels, followed by "Electrolux" uprights in 1967 and tanks in 1968
Both double and triple digits were used through 1979.
**some with a second letter indicating a country's modification (each had its own)
See Electrolux Canada "Letter Prefixes" for meanings. I believe the 'Z' is still used by AB Electrolux of Sweden and its North American subsidiaries.
SINGLE BRUSH POLISHER
B2—1918-1926
TRIPLE BRUSH CLEANERS (credit to 'Gugue' on Flickr)
B3: 1927-c.1933; (aluminum/black)
BA4: c.1934-c.1950; (black--dappled in dark green or graphite dappled in green; France—dappled in coffee brown or red); nickel-plated adornments on the triangle which are the fittings for the brush pulley bearings and another design for the bottom bumper.
BB4: c.1934-c.1950; (black--dappled in dark green or graphite dappled in green)
France—dappled in coffee brown or red); nickel-plated adornments on the triangle which are the fittings for the brush pulley bearings and another design for the bottom bumper.
BC4: c.1934-c.1950; (black--dappled in dark green or graphite dappled in green)
B6: c.1950-c.1960; (grayish green or metallic green)
B12: c.1965-c.1970; (green, silver, or metallic golden)
*B17: c.1965-c.1970; (orange/royal blue base, light gray top/chrome base, black top/white base)
B107/”Lux”: c.1965-1980s; economy; (B4-style; gray, orange, or beige Bakelite)
B18: c.1970-c.1982; plastic handle
*B19 c.1970-c.1982; (sage green top/white base); plastic handle
B23: 1982-1992; (coffee brown top/orange or beige tan base, dark gray top/light gray base, or dark green top/white base); plastic handle
*B25: 1980s & 1990s
*B26: 1980s & 1990s
*B27/"Lavencera": 1980s & 1990s; (brown & chrome or polished aluminum)
*B53:
**B63S/”Ono”/”Mundial”/”Lady Lux”: circa AB Electrolux's 90th anniversary & after; (light gray, cobalt blue, or black)
**B95S: c.1992-c.2000 (gray, dark gray, black/red, dark green, or black)
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Lux International (the vacuum cleaner division of AB Electrolux of Sweden from 1919 to 1998.)
Triple Digits—1998 to present
D Prefix—?
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Some information may be inaccurate, but it's close. Any corrections or additions are welcome.