Omega Seamaster Automatic 120 ‘Big Blue’ Ref. 176.004 1970s Caibre 1040

176.004, aka “BIG BLUE” stainless steel chronograph, the ultimate tool watch. C. Three-body, brushed, unidirectional revolving graduated bezel for decompression timing, screw-down case back and crown, case back with the Seamaster logo.

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