No way to tell this as it was a "Silent" change by Meridian just after first release.
Only M know this by serial number, but according to Paul Webb and Chris Cope they do still have a quantity of version 1 available.
It is a matter of personal choice related to the headphones you have.
After initial purchase on Explorer release I auditioned version 2 but prefer version 1 with my Grado cans.
Hector

AV: Thorens TD160B, SME, ShureV15MK2, 500, 598, 861v4, DSP7200.1, DSP3300HC Samsung UE55, SkyHD.
DINING: MS600, AC200, DSP5200SEUG.
STUDY 504, Roon Nucleus + RevB, 808v6, 5200SE, Mac & PC (Touch Screen), Prime+PS Grado GS1000i
HORIZONTAL: M80, MS200, Red Rose Spirit + Sonus Faber Toys, iPad Mini
A capella to Zydeco