Check the listing for details. Antique Brass Mathematical Drafting Tool Instrument Steel Screw. Condition: Used. Listed at 20.00 USD. The Antique Brass Mathematical Drafting Tool Instrument Steel Screw is a rare and collectible piece that would be a valuable addition to any engineering or drafting tool collection. This instrument is designed with precision and accuracy in mind, as it would have been used for intricate calculations and measurements. The antique brass construction adds a touch of history and nostalgia to the tool, making it not only functional but also a unique decorative piece.