This Omega Speedmaster Professional, ref. 3872.50.31, has a plexiglass front and a sapphire glass back. The leather strap distinguishes it from the more common 3572.50.00, and it was replaced by the 'sapphire sandwich' in 2004.
Movement Type
Manual Chronograph
Caliber
1863Jewels
18
Reserve
48
Frequency
21600
Hands
Small Seconds
Shape
Round
Lug Distance
20.00 mm
Material
Stainless Steel
Glass
Plexi
Diameter
42.00 mm
Water Resistance
50.00 m
Dial Color
Black
Material
Leather
