The $5 bill displayed for decades on Charles Fairbanks IV's wall was long a treasured family heirloom from Alaska. Now, to the surprise of the grandson of a turn-of-a-century vice president, it's also become a likely treasure trove.

The rare find is expected to fetch as much as $300,000 at auction this month when a Texas auctioneer plans to put it up for bids in Dallas and online as part of the American Numismatic Association National Money Show.

The bill was presented in 1905 to Vice President Charles W. Fairbanks - Theodore Roosevelt's No. 2 - and was from the First National Bank of Fairbanks, Alaska. The family has had it in their possession ever since and recently decided to auction it off through Dallas-based Heritage Auctions...