Pictures reveal whether the transformer is oil-filled or dry-type, the number and arrangement of radiators or cooling fins, presence of fans or pumps, and whether there is a conservator tank or sealed tank design. Bushing size and geometry hint at voltage levels, while OLTC compartments and cable boxes show connection types. Placement of temperature gauges, oil level indicators, and monitoring sensors can also be seen, giving clues about how cooling and condition monitoring are implemented.