Joe Vitale's book _There's a Customer Born Every Minute: P. T. Barnum's
Secrets to Business Success_ has a brief history of the Cardiff Giant
case (p. 17-18).  If Joe is still on the Forum list, perhaps he can
provide the best primary sources detailing the story which began in 1869
and ended up in court with two hucksters suing each other for fraud.

It is possible Barnum may have detailed his own version of the case
in one of his autobiographies but they are not indexed and I didn't
find it in a brief check of the 1870 edition.

Barb