Actually no I'm wrong and I'm having a forgetful moment from my days on head-fi. My original CAL had bio-cellulose coated dynamic drivers. Sony were the first to my knowledge to engineer and use bio-cellulose drivers in the mid 1980's flagship Sony MDR-R10 headphone. The bio-cellulose drivers were again used in the 90's with there MDR CD1000 and CD3000 high end headphones, both of which I've owned. The bio-cellulose coating was very hard to engineer properly laid over a headphone dynamic transducer due to it being akin to a layer of bacterial formed organic mask and the drivers in some Sony headphones grew mold and would deteriorate though stored in bad environment conditions but was quite rare of a phenomenon (seen 3 counts of this in 1 R10 and 2 CD3k headphones). I believe Foster (parent company of Fostex and an OEM) manufactured the drivers for CAL headphones and certain Fostex headphones using the bio-cellulose drivers.