The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
Wikipedia's[2] Overburden Conveyor Bridge F60 article dates the first unit's construction to 1969-1972 and entry into service at the Welzow open-pit mine to 1972, without a specific day.
Documents the first F60 being built 1969-1972 and entering service at Welzow, and lists the F60 units still operating today.[1]
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