The date a mark was first used anywhere. In the United States, the first person to use a mark has priority, and can exclude all subsequent users of identical or confusingly similar marks. For this reason, it is important to document the date of first use of a mark. This may be done by taking a dated photograph of the goods bearing the mark or keeping the original advertising if it shows the date that the ad ran. It is also a good idea to keep records of the first sale of goods or services made using the mark. This may include a bill of sale or invoice showing the purchase of advertisement or a mailing.