If you're older than, say, 35, you probably have heard of the 78 RPM record, even if you haven't actually heard one.
The 78s heyday was in the first half of the 20th Century, before they gave way to LPs, and 45s, and later eight-track tapes and cassettes, and then CDs and mp3s. If you see 78s today, it's likely in a thrift store, a rummage sale, or your grandparents' attic.
But there are some who see great value in the 78, both for the audio it produces and for the artists whose work might be lost forever, if not for the handful of copies of their songs that still exist.
"Because 78 RPM records are so fragile and because nearly no metal masters survived of those sessions, the 78s themselves, the artifacts, the records, are sometimes the only evidence we have that these songs were ever written," says author AmandaPetrusich.
The scarcity of these records, and the unique world of 78 collectors, are the topic of a new book Don't Sell at Any Price: The Wild, Obsessive Hunt for the World's Rarest 78rpm Records by Petrusich, who traveled from Key West to the Milwaukee River in search of the 78s allure.