During this time, the Mint began a partnership with the General Mills company, in which 10,000,000 boxes of Cheerios cereal would contain a 2000-dated Lincoln cent as a prize, one in every 2,000 boxes would contain a new Sacagawea dollar and one in every 4,400 would hold a certificate redeemable for 100 Sacagawea dollars. It was later discovered that the dollars included in every 2,000 boxes were in fact early strikes, differing from those ultimately issued for circulation by the number of tail feathers on the eagle. Approximately 5,500 of the coins were included in the boxes of cereal. Far less of these dollars are known, since many may have been spent and entered circulation. Later analysis also showed that an unknown number of them had the normal "Reverse of 2000" rather than what collectors called the enhanced tail feathers "Reverse of 1999". Thus the fact that a coin came from the cereal box does not guarantee that it is the rare variety.