I think I read somewhere that throughout the '60's and into the '70's, many swivel chairs such as the HM Eames Aluminum Group and Knoll Pollock office chairs were made with the 4-star base. Then, sometime in the '70's, the government required such chairs to be made with the 5-star base we see today. I guess it was supposed to be more stable. I was wondering if this was accurate, and if so, what was the year this requirement was imposed? Knowing the year would help date some chairs I have. Thanks.
Yes, it's true...
... but the safety regulations changed at various times in different countries, and manufacturers implemented the change gradually throughout the 70s and 80s. For most manufacturers, there wasn't even a sharp transition from 4- to 5-star base across all product lines, let alone a sharp transition worldwide or across any country, so the base style probably won't tell you much about your chairs' date of manufacture.
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