HELMSMAN COMPASS UNIT KEY PART NO. NUMBER PART NAME DESCRIPTION QUAN. 1 13D1 Dome, Models HB-70, 71; HF-72, 73; HD-74, 75 1 2 13D2 Dome, Model HV-77 only 1 3 13D1G1 O-Ring, Dome 1 4 13J1X Dial Assembly (Open Face) Models HB-70, HF-72, HD-74 1 5 13J2X Dial Assembly (Direct Reading) Models HB-71.  HF-73, HO-75.  HV 77 1 6 13H1X Gimbal Ring Assembly 1 7 13K1X Lubber Line Pan Assembly 1 8 13H1Z1 Tab, Balance (For Open Face Dial Assembly) 1 9 13H1Z2 Tab, Balance (For Direct Reading Dial Assembly) 1 10 9H1Z1U1 Retainer.  Balance Tab 1 11 13C1 Bowl 1 12 1C1B1 Screw, Fill Plug 1 13 4C2R1G1 O-Ring, Fill Plug Screw 1 14 13N1 Diaphragm 1 15 13N1U1 Retainer, Diaphram 1 16 13G1J1 Magnet, Compensator, Models HB 70.  HF 72, HD 74 4 13G1J2 Magnet.  Compensator.  Models HB-71, HF-73.  HD-75 4 17 13G1P1 Rod, Compensator, Models HB-70, HF-72, HD-74 2 13G1P2 Rod, Compensator, Models HB-71, H-73, HD-75 2 18 13G1L1 Cover, Compensator 1 19 13E1B1 Screw, Compensator Cover 2