PHILADELPHIA, March 7 — An unknown number of new George Washington dollar coins mistakenly struck without their edge inscriptions made it past Mint inspectors and are fetching about $50 apiece online.

Properly struck coins are inscribed on the edge with “In God We Trust,” “E Pluribus Unum” and the year and a mint mark. The Mint struck 300 million of the coins, which are gold in color and slightly larger and thicker than a quarter.

The coins went into circulation Feb. 15. About half of them were made in Philadelphia and the rest in Denver. Reports of error coins have come only from Philadelphia, Becky Bailey, a Mint spokeswoman, said. Ms. Bailey said it was unknown how many coins lacked the inscriptions.