Greenville firm behind world-record sale at auction.

• Position: Richmond Auctions of South Carolina, Musgo Gasoline

Looking for a sign? In the case of this petrol-themed one, you are too late.

Greenville-based Richmond Auctions set a new world record recently for the most expensive antique advertising sign sold at auction.

A 48-inch double-sided porcelain Musgo Gasoline sign sold for $1.5 million (including buyer's premium) shattering the previous record of $400,000, according to a news release from Richmond.

Considered the Holy Grail of antique advertising signs by most collectors, the sign was discovered in an attic in Michigan, the release stated. It had never been seen by the public and was a fresh to market example.

Musgo, originally located in Muskegon, Michigan, was believed to be open for less than six months during the mid-1920s, according to the release. Following its closure, most of its signs were used as septic tank lids causing one side to decay from septic fumes. This record-breaking sign was new old stock, never used as a septic tank lid, and is the best-known...