Pack of "Solidox" dental soap, pack made of cardboard. A copy of the product sold in Germany in the 1930s. "Solidox "was a "transitional link " between the dental powder in boxes and toothpaste in tubes.
You can use this dental product to brush your teeth during reenactment! The composition is glycerin base and tooth powder. Just wipe it with a damp brush to make a foam and brush your teeth with the foam. Or bite off a piece and rub it with a brush into your mouth with water. Of course, brushing with ordinary toothpaste is more pleasantly. But where to get it in the trenches, comrade?