This field is located on the Main tab of Customer Maintenance when you click the POS hyperlink in the far right column.
This field determines whether or not a customer is eligible to get special promotions of type 1. Special Promotions (1) are set up in the promotion subsystem just like any other promotion, but they are identified to the system as "special promotion type 1" by entering the promotion's first 1-8 characters in option 8263 "Special Promotion (1) Indicator." For example, if you set this field to Yes for a particular customer, and option 8263 is set to SPRING, then this customer would be eligible for any promotion that starts with the letters SPRING.