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公开(公告)号:US2119862A
公开(公告)日:1938-06-07
申请号:US17436137
申请日:1937-11-13
Applicant: BLACK ROCK MFG COMPANY
Inventor: KELLER JOSEPH R
IPC: B24B21/02
CPC classification number: B24B21/02
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公开(公告)号:US2048634A
公开(公告)日:1936-07-21
申请号:US5301935
申请日:1935-12-05
Applicant: BLACK ROCK MFG COMPANY
Inventor: KELLER JOSEPH R
IPC: B24B5/04
CPC classification number: B24B5/04
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