Use of NS bolts with two gas holes

When was the nickle steel bolt with two gas relief holes first used? TIA

If you are asking about the nickle steel, the change was made at #1,275,767. If you are asking about the holes, I can't help.

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Originally Posted by RBruce

When was the nickle steel bolt with two gas relief holes first used? TIA

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Very early 1937.

Happy Holidays! :wave:

J.B.

Thank you bb1 and John.