When you see a dial of approximately 40 yeas old Seiko watches carefully, you might find a star mark.
This tells you what material is used for indexes on dial..
For example, the first Grand Seiko's(3180) indexes are made by SD type dial.
Special Dial (SD)
The indexes are made from solid 18K or 14K.
The second Grand Seiko's (57GS) indexes are made by AD type dial (except for early 57GS)
Applique Dial (AD)
Indexes are made from Seiko Gold Plated(SGP) or Rhodium plated on brass
Some Seiko Crown indexes are made by ED type dial.
Extra Dial (ED)
Normal Gold plated or Nickel plated on brass.
Domestic watch Series No.1,3 Tombo Shuppan, Yoshio Nagao,Toshiki Mori 1996/6