1969–c. 19723 variants
Round-case El Primero chronograph with overlapping blue, grey and anthracite registers and a date at 4:30. Collector-recognized Mark 1, 2 and 3 cases differ in their lug junctions and backs; component combinations matter more than a serial number alone.
Introduced in 1969. Specialist guides date original-reference production approximately through 1972; individual executions may have narrower ranges.
Production years have not been recorded for these variants.
Early case with a smooth transition from the lugs to the case top and a plain back. The documented tricolour-dial specimen has a faded blue register and is shown on a signed leather strap.
Grooves distinguish the lug-to-case junction, while the back remains plain. The photographed example has tricolour registers and a Gay Frères ladder bracelet; the dealer describes its case as unpolished.
Grooved-lug case with a four-point star back and an A Under H dial. The documented specimen has broad register hands, a large-circle crown and a Gay Frères ladder bracelet with ZJ endlinks.
Specs shared by all variants. Variant pages show where a variant differs.