The Great T206 Back Stamp Project

This is a neat stamp that was used as a coupon of sorts in a store.  It reads:

ACCEPTED

Less 12% trade discount, and

in 10 days   Net 30 days

The same concept is used today, although it is more typical to see 10% or 15% in 10 days and Net 30.  This of course refers to the customer taking 10% or 15% off their invoice if paid within 10 days otherwise the full invoice is due within 30 days.