"If you believe that, I've got a bridge to sell you"

trying to find this expression and it's origins for a friend. "If you believe that I've got a bridge to sell you" or ..."I've got a bridge for sale."
We believe its regarding the Brooklyn Bridge, but can't come up with a date of first usage.
any help would be appreciated.
thanks.

Back in the 1970s, conmen went in for scams selling London bridges - usually they would pretend to have authority to sell Tower Bridge. To cap it all, some American did actually buy the original London Bridge - which wasn't particularly attractive, but IMO culturally wrong to do.

it is almost as bad as selling the Ponte Vecchio in Florence would be.

thank goodness for the decency of a German WWII officer who defied orders telling him to blow it up. also happened in Paris, from what I recall.

anyhow, only an idiot would be taken in by a conman selling a land-mark - hence the expression about selling somebody a bridge.

L