此款極座標式求積儀是由英國倫敦Elliott Brothers公司製造，型號為18006。該求積儀的固定桿與追蹤桿是不可拆解的，但追蹤桿的長度可以調整。追蹤桿上帶有用於蒸汽指示圖的測量點，使該求積儀特別適用於蒸汽機的性能分析。

This polar planimeter was manufactured by Elliott Brothers of London, model No. 18006. The fixed rod and tracing arm of this planimeter are not detachable, but the length of the tracing arm can be adjusted. The tracing arm includes a gauge point specifically designed for steam indicator diagrams, making this planimeter particularly suitable for performance analysis of steam engines.