A group of French mathematicians, collectively named Bourbaki, set out to compose an international system of units (SI) beginning in the 1930s. Using the German word for 'integers', Zahlen (singular - Zahl), 'Z' was chosen as the symbol for them.
AB Electrolux's use of the 'Z' in this way is only a theory on my part, but it makes sense; it also explains why the company began using a Z prefix for its vacuum cleaner model IDs in the 1930s. The B prefix had already been in use with the floor polisher model IDs, likely to represent 'buffer' or 'beautifier'.
I actually contacted AB Electrolux some time ago and asked its rep what 'Z' meant, but he had no idea and found no one else with the knowledge and nothing in company resources to explain after several days checking into it.
In the general US population, we occasionally will use a hashtag symbol in the same way as ABE supposedly used a 'Z'; so Z65 in Sweden would have been #65 in the US according to my theory.
Electrolux Corporation (US) used no vacuum cleaner model ID prefix until 1994 (C-canister, U-upright, S-Sidekick mini nozzle, L-Little Lux hand vac). A letter suffix was also added in 1994 to differentiate the original design and/or styling from the updates. Due to initially importing floor polishers from Sweden, exec's continued using the B prefix for its floor polishers/rug shampooer model IDs when it began manufacturing them in 1959; using an 'S' for Scrubber/Shampooer beginning in 1994.
