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Standards and conventions for mechanical drawing (1921)
Kepler, Frank Roy, 1875-, Detroit (Mich.). Board of Education · [Detroit] · leaf 30
US. sra FORM SQUARE PLATE 13 28 ^ DR/UL 6 DRILL SCRCV>/ THREADS wm7A r/e i. DRILLED HOLES wm^ r/a a AMechanical drawing
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