Casio BG-390 Manual — Modules 1678 / 1668 / 1808

Seven owner's manual PDFs for the Casio module 1678, each a different scan (English included). Casio fitted it in the BG-390. The same documents also cover modules 1668 and 1808. For module 1678, Casio's spec sheet lists one SR1120W and a SR621W (for EL) backup cell, with 15 months of battery life and accuracy within ±15 seconds a month; the module first shipped in May 1997.