In total there are at least five versions of the 007. Here comes the list but the serial numbers are just approximations. No idea when the actual change took place. 1: 70xxx serial number, first version with the large frame drivers and carbon fiber case. 2: 71xxx serial number, simplified driver frame for easier assembly, new materials on all "soft" parts 3: SZ1 and BL version: Some small changes around (cable entry for instance) but the biggest problem was the QC with these so the sound is hit and miss. Mostly miss compared to the first version. 4: SZ2, the first Mk2/A units. New earpads, headpad, cable entry. Earpad spring is raised to help comfort and a port is added to eliminate the fart. The drivers are pretty much the same as Mk1 so these can be modified. 5: SZ3, identical to the SZ2 but new diaphragm material and the port has been improved. Introduced in mid to late 2009 and the model in current production now. No hope of rescuing these through mods.