Agree about the Zos, I bought one on ebay delivered for about £85 (the price varies due to currency fluctuations). It was ok I used it on an S400, but not sure it was springer rated and they are very heavy. They are also marketed under a number of different names. I had doubts about it so moved it on. The BSA if a genuine one will be springer rated.
EV2 mk2 with 2009 big Nikko
HW97K with 6-24 Nikko Nighteater