Ever since the Chinese are selling goods on eBay and AliExpress, electronic parts have been polluted with fake and inferior parts.
Often casings are created and copied like the original parts but filled with dummy or inferior internals.
We do our best to let these fake parts not enter our stock by only buying old stock from companies that have started way before the
turn of the century.
Rod Elliot has a nice site where he describes a lot of fake parts he encountered and how to spot fake parts.
https://sound-au.com/counterfeit.htm