https://www.datamp.org/ Recently added patents en-us https://www.datamp.org/patents/displayPatent.php?id=59214&pn=388,007 Clamp Screw Patentee: Pardon A. Whitney - Southington CT Granted:1888-08-14

Malleable "wing nut" type head pinned to a steel screw; this makes a more durable screw for "C" or bar clamps. This improvement was incorporated into clamps produced by Peck, Stow & Wilcox, including "C" clamps with bodies corresponding to design patent D18,376 and patent 385,983. -- See DATAMP entry for D18,376 for photos, 1890 product description, etc. The patent date appears in some adjusting screws corresponding to this patent.
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