I am a member of the Stereoscopic Society (http://
www.stereoscopicsociety.org.uk), you may have seen my postings on
their meetings and maybe even seen stereos I have taken at Hackspace.
There are a number of their members who have knowlege about and
collections of Victorian stereos, one in particular, Bob Aldridge,
would be able to give a very good interview, but I know he has limited
time. I will be contacting him over another matter and ask if he would
be willing to help you.
Martin