Text copied from TM E 30-451, March 1945 :

"200 Gram slab. "sprengkörper 28" This slab is provided in two forms; in waxed paper and in a bakelite case. The waxed paper slab may contain either TNT or picric acid. Pressed picric acid is contained in the casing of two bakelite mouldings. The bakelite slab actually weighs 250 grams or 8 3/4 ounces".

50mm x 70mm x 40mm

The bakelite version of which the text speaks can be found HERE.