In cataloging terms, usually stands for Year-Month-Date .
Many Japanese sellers don't ship internationally. Services like ZenMarket or Buyee are essential. yapoo market ymd 86 11 hot
Many items marked with these specific date codes were produced in limited quantities. As the years pass, "Deadstock" (unsold, original condition) items from late '86 have become the "holy grail" for collectors. In cataloging terms, usually stands for Year-Month-Date