The H052 and H072 are 10 hole with the top and bottom hole being 11 5/16" apart and holes at 8 o'clock and 4 o'clock are 11 1/8" apart. They are 3/4 and 1 ton late 46 until 1972. 1/2 ton are 10 hole with top to bottom 9 15/16' and 4 o'clock to 8 o'clock 9 1/4" used from late 46 to 62. This is the bolts of the third member to the banjo housing. The 12 bolt refers to the rear cover. The 12 bolt cover came in 3.40 and 3.07 ratio for half ton and 3.73 and 4.11 for 3/4 ton and came out in about 69. The earlier 3/4 and one ton were offered with 4.11,4.57, 5.14 and 5.83. Half ton were offered in 4.11 and 3.90.