Most, if not all, of Aalto's recently produced pieces were produced by Artek. Alvar and Aino Aalto founded Artek for this purpose. If it is a replica, then it does not really matter who produced it, nor is it likely that you will be able to find the producer, as they were copying Aalto's design.
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fbx, curious to know why you described your chairs as replicas. If the purchase year you mentioned is accurate (1980s), there was no market for replicas back then when retro 20th century modernism & later mid century modern was still in its infancy. It is either these were purchased new through contract only showrooms with an architect or interior designer in tow or these were acquired vintage usually by the creative bohemian types who did not look down on used or secondhand stuff.
Even if these were acquired in the mid 1990s (the decade of reissues), these are still authentic as Zephyr noted, these chairs were in continuous production by Artek since the mid 1930s.
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