Graphite Block 4 pieces

Description

4 Graphite blocks, as shown. Have grooves and holes in them unknow what previously used for.  Blocks measure approximately 9"x2"x1", 8"x1"x1/2", 3"x2 3/4"x 1 3/4", 2 1/4"x1 1/2"x1 1/2".
Please look at photos, message with questions.