Casio VDB-100 / VDB-1000 Manual — Module 658

Two owner's manual PDFs for the Casio module 658, each a different scan (English included). Casio fitted it in the VDB-100 and VDB-1000. Casio's spec sheet lists one CR2016U, with 18 months of battery life and accuracy within ±15 seconds a month; the module first shipped in Feb 1991.