Keuffel & Esser 68 1617 (4053-3) 10″ Polyphase Mannheim DMS Trigonometry Scales68 1617 (4053-3) 10″ Polyphase Mannheim – 94132468 1617 (4053-3) 10″ Polyphase Mannheim – 201058D Series – Decimal Trigonometry ScalesD68 1617 (D4053-3) 10″ Polyphase Mannheim – 030078D68 1617 (D4053-3) 10″ Polyphase Mannheim – 660040