The Seiko Prospex SRPH99K1, known as the "Black Series Tortoise", is a limited edition automatic watch with a robust, land-oriented design. 

Movement

• Caliber Number: 4R35
• Movement Type: Automatic with manual winding capacity
• Power Reserve: Approximately 41 hours
• Jewels: 23
• Frequency: 21,600 vibrations per hour (6 beats per second)
• Functions: 3 hands, date display, stop-seconds hand function 

Case and Dimensions

• Case Material: Stainless steel with black hard coating (PVD)
• Case Shape: Round, "Tortoise" cushion-shaped profile
• Case Diameter: 42.4 mm
• Case Thickness: 11.7 mm
• Case Length (Lug-to-lug): 45.2 mm
• Water Resistance: 200 meters (20 ATM), suitable for swimming and diving
• Crown: Screw-down
• Case Back: Screw-down 

Crystal and Dial

• Crystal Material: Sapphire crystal (scratch-resistant)
• Dial Color: Matte dark grey/black
• Luminescence: Green Lumibrite on hands and indices
• Bezel: Unidirectional (or bi-directional, sources vary) rotating black IP stainless steel bezel with a compass scale insert 

Strap and Other Features

• Band Material: Black fabric/polyester strap
• Band Width: 20mm
• Closure: Buckle
• Limited Edition: Yes, 7,000 pieces worldwide
• Additional features: The case back is decorated with ground-to-air emergency signal codes.