Found this 1970 edition French clothing catalogue at a antique shop.

Grape fruit, orange and lemon marmalade

 1 Large Grapefruit

2 Large Oranges

2 Lemons

850ml Water

1.8kg Sugar

Wash the fruit and cut into four.

Put fruit in a pan with the water and simmer for 1 hour

Remove the fruit and cut up finely, discarding the pips.

Return the chopped fruit to the pan containing the liquid.

Add sugar and heat gently, stirring occasionally until the sugar has dissolved.

Bring to a full boil until setting point.

Remove from heat, allow cooling then pot and cover in the usual way.