An all-rye, unleavened loaf. It’s a bit like Irish brown bread, which is also unleavened but is made with wheat flour. Roggebrood is essentially steamed, then put back in the oven to dry somewhat.
Here’s a mention of what is almost certainly roggebrood (given that it’s listed separately from the cheese sandwiches, which likely would’ve used a leavened dark bread) from the November 15, 1894 edition of The (New York) Evening World:
The Dutch Supper
The “Dutch supper” has become popular for after-theatre fests:
The beer or ale for these suppers is served in large German steins, and these are a picturesque adornment to the round table. No cloth is spread, but the highly polished board is decorated with dainty covers at each plate.
A red light is effective with these decorations, and red ribbon used to tie the napkins adds a pretty bit of color to the table.
(a solid brick of un-leavened rye; slice thin)
2 c. of potato water from boiling 3 or 4 diced-up potatoes
1/2 c. molasses
1 T. salt
1/2 c. brewer’s yeast–for taste only
2 T. caraway seeds, ground
7 c. of rye flour
Pour boiling potato water over all other ingredients in a large bowl. When dough has cooled, blend all ingredients. Spoon dough into 2 medium greased loaf pans. Smooth surface.
Cover pans with foil and place them in a pan with hot water for 10 minutes. Cover big pan also with foil; steam in slow oven, 250 deg., for 3 hours. Then remove large pan from oven and empty.
Remove foil from loaf pans and return to the oven for another hour. [Original says “Turn off heat,” but I believe is an error; ignore it and proceed.]
Remove bread from pans but return to the oven for another hour. Turn off heat. Remove bread from pans but return to the oven to dry out (1 hour).
Enjoy very thin slices with butter, ham, cheese, or jam.