Zerostat: Old is Gold?

I was recently in the market for a Zerostat gun.  I looked online and saw that they had moved their production from England to China.  Of course, without any reduction in price.  As I try to avoid Chinese manufacture as much as I can,  I thought I would buy a used one on ebay.  I bid on a few auctions but was surprised to see them selling for around $50 for one in decent (but hardly new) condition.  The new blue Zerostats from China are $80 and up. 

Are the old Zerostats in some way superior to the newer Chinese made that would justify the (IMO) relatively high prices being realized for the original guns?