tonne, thousand kilograms, (kokuji)
瓲 centers on a metric unit of mass: a tonne, equal to one thousand kilograms. It is a Japanese-made character (kokuji) created specifically for this measurement.
瓲 is a Japanese kokuji created by combining 瓦 (tile, used here as a unit-of-weight radical) with 屯, which likely contributes the phonetic element トン. It was coined to represent the metric tonne.
瓦 often appears in characters for units of weight (like gram), and 屯 suggests the sound トン. Together they form a tonne: a heavy weight made of tiles.
For トン, the reading is exactly the English word 'ton'. Picture a ton of tiles (瓦) piled up: ton -> トン.