Short answer
Do not date a liner photograph from one feature alone. Combine multiple structural and operational clues, then compare them with documented refit dates.
Useful phase markers
FunnelsHeight, caps, color schemes, smoke deflectors, and even the number of funnels can change over a ship’s career.
Bridge and wheelhouseEnclosed bridge wings, altered fronts, radar platforms, and navigation equipment can sharply narrow a date range.
Promenade enclosuresOpen promenades were frequently enclosed or glazed during refits, creating obvious chronological markers.
Lifeboats and davitsBoat count, boat type, davit style, and their arrangement often changed after regulation or wartime experience.
Masts and aerialsWireless aerials, mast height, radar, signal equipment, and cargo gear are useful technological indicators.
Paint and ownershipHull color, funnel livery, neutrality markings, wartime camouflage, and renamed ownership can identify broad phases.
Start with changes that cannot be temporary
Deckhouses, bridge structures, promenade enclosures, and major machinery-related alterations generally provide stronger dating evidence than deck chairs, awnings, flags, or boats that could be moved or changed temporarily.
Use the background too
Port infrastructure, tugboats, pier configuration, nearby ships, automobiles, signage, and photographic format can independently constrain the date. A photograph should be treated as an entire evidence object, not just an image of the ship.
Attribution rule: if the visible evidence only supports “after the 1923 refit and before the 1928 alteration,” preserve that range. Do not manufacture a precise year.