How can independent clues narrow a date range?

Evidence can narrow a historical date without identifying an exact year. A lower bound rules out earlier dates; an upper bound rules out later ones. Combining accepted bounds means keeping the dates that satisfy all of them, an intersection rather than an average.

For the invented depot, base clues put completion from 1902 through 1910, including both endpoints. An original built-in fitting was first available in 1902, while a securely dated 1910 image shows the building complete. Under those assumptions, completion cannot be earlier than the fitting’s availability or later than the image.

An additional original bracket first available in 1904 raises the lower bound to 1904. An independent, securely dated 1908 survey showing the completed depot lowers the upper bound to 1908. Together, the accepted clues leave 1904–1908. Every year in that interval remains possible; the middle year is not established merely because it lies halfway between the bounds.

Each constraint depends on the evidence being correctly dated and identified. The built-in-item argument also depends on original placement: a later replacement would not establish the building’s earliest completion. If the bracket identification is disputed, that bound is removed and the range widens to 1902–1908 while the accepted survey still applies. Independent clues can narrow uncertainty without guaranteeing perfect accuracy or an exact date.