Found a Contract expenditure for Drillmation Inc for Bolts and M2 Carbines $1,657,113 listed in a Army Research and Development monthly newsletter dated March 1966.
Listed under RDTE production contracts, Which I assume means Research and Development Test and Evaluation: RDTE.
It reads: Drillmation, Inc., $1,657,113, bolts for M2 carbines
This limited information can be found on page 17 in the upper middle column:
https://asc.army.mil/docs/pubs/alt/a...6/Mar_1966.PDF
Thought it was better to add like this, instead of reviving a ~10 year old thread.
These are a Round Bolt with the gas hole on the bottom and a D stamped on the left lug.
There was some debate over the type of finish and who they were made for?
M and D marked post WWII Round Bolts:
https://www.milsurps.com/showthread.php?t=30148Information
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