While it may sound unlikely, thousands of collectors of gas station memorabilia from around the world are meeting in Des Moines. The 14th Annual Gas Petroleum Collectors Convention, Swap Meet & Auction is filled with things from bygone eras — old-time gas pumps, soda bottle dispensers and oil cans dating back decades, selling for hundreds of dollars. Convention organizer John Logsdon of Urbandale says the most unusual piece at this year’s nostalgic gathering is about 80 years old.It’s an arrowhead-shaped sign for Rand McNally Road Atlases which he expects to sell for at least 13-thousand dollars. One big auction will be devoted just to oil cans. Logsdon says those once-common tin cylinders can be pricey too, ranging up to 900 dollars.The convention is underway at the Des Moines Airport Holiday Inn through Saturday.