Your right I was mistaken,
Rear Sight Lock Nut N/A Type 1 January/1936 to March/1942 1 - 530000 Flush nut, short pinion, 6-40NF thread
Elevation Knob N/A Type 1B June/1940 to September/1942 46000 - 850000 No part number, checkered rim with closed arrowheads.
Elevating Pinion N/A Type 1 January/1936 to March/1942 1 - 540000 Short with 6-40NF thread, with flush nut.
I should have checked..
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