The sale, which represented 22 percent of the company, raised $46.75 million for Marketwatch.com.
The sale has raised more than £1m over the past 17 years.
It estimated the sale would raise at least $200 million.
But the potential sale of the house raises an important question.
At $13 a share, the sale would raise about $71.5 million before expenses.
Art experts say a sale could raise more than $5 million.
At that price, the sale could raise more than $4.4 billion.
The sale would raise some $1.4 billion in new cash.
The first such sale took place in 1769 and raised £564.
The second sale occurred in March 1788 and raised £529.