Greg,
James or the "Famous James" as they were more commonly known started in
the 1880's by Harry James they were floated on on the stock market in
1897 and he was their first director but only for a short time.
They were regarded as very good bicycles and made their own two speed
gear, they made everything solos, tandems, tricycles in both utility and
sports models and were popular with club folk and racers up until the
30's.
Most people remember their motorbikes now and they had some racing
successes with these as well, Bert Kershaw won the 1929 Belgium GP on a
James fitted with a 172cc Villiers Brooklands engine running on alcohol
(just like me!). They also made speedway machines with their own 496cc
V-twin ohv engine. On the continent Karl Arbarth the famous car designer
raced a James motorcycle.
Your tandem could be that early as they were relly popular in the 20's
you only need to look in old copies of Cyclings from that decade to see
all the tandem adverts.
Here is a good link which will explain history etc mostly motorbikes.
http://www.classicbikeguide.com/
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Michael Francis Butler
michaelbutler@fastmail.fm