The wording on the ashtray is:
The Mikado, Japanese & American Cuisine, 70 Jack London Square, Oakland
The decryption here is of then future Zodiac Killer’s victims numbered 17, 18, 20, 21 according to page 309 of Robert Graysmith’s book Zodiac (Titan Books, London, 2007).
Appear his next Zodiac Killer victims:
Donna Lass, Missing Person, suspected foul play, since September 26, 1970.
Mary Bennallack murdered on October 25, 1970.
Lynda Kanes killed on February 26, 1971.
Betty Cloer slain June 19, 1971.