A Bicycle Built for Two?

I have walked past this showroom so many times, but this velocipede drew me inside for the first time.

Built in the 90's by Soceadth (sounds Gaelic, but a Japanese company) the dealer told me that it is based on an original design from the early 1900's.

Unfortunately my research has not been able to confirm this.
Edit:
Thanks to Peter I have now found this one from the 1890's

Edit:
Potential Design Flaw

Surely both riders would have to be of a similar size/weight or the balance of the thing would be compromised?