The chopped strawberries are preserved with sugar and chopped raisin.. The sugar draws out the moisture to produce a thick syrup along with shrunken strawberries and softened raisins. This is a really neat product that deserves revival.
It can be served as a sweet chutney and also used as an ingredient in baking. Also think that this product may well be superior to frozen berries which are best served by grinding up or cooking anyway.
My experience with frozen raspberries and frozen strawberries has always been that they were a poor compromise and took effort to improve. This product, even stripped of the raisins and surplus syrup could be quite nice.
Again an aging process takes place here in which the water is drawn out. This could even be successfully dried as well.