Any LCD-2s with serial number starting with 54 or higher should have Fazors. Any starting with 53 (and a few starting with 56 from the early days) will be a pre-Fazor model unless the drivers were serviced after the beginning of Fazor production, which began in January 2014.
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Any LCD-3s with serial number starting with 27 or higher should have Fazors. Any starting with 26 will be a pre-Fazor model unless the drivers were serviced after the beginning of Fazor production, which began in January 2014.
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To the best of our knowledge, all LCD-Xs and LCD-XCs should have Fazors installed, since those headphones were launched at the beginning of Fazor production in January 2014.
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The best way to check for sure is to feel for the Fazors inside the earcup: if you feel a flat metal stator plate with openings in it under the mesh, your headphones have no Fazors; if you feel the tips of triangles, those are the Fazors themselves.