Brand: Timex
Model: Timex Marlin Calendar
Reference: 27820
Caliber: M105 (Manual Wind, date window)
Year: 1980
Dial Code: 27820 10580
Manufactured: Great Britain
Case: Gold plated
Lug Width: 18mm

The closest catalog reference i have for this vintage Timex Marlin Calendar was one year later in 1981 reference 2782 10781