Casio DW-310 / DW-240 Manual — Module 690

Three owner's manual PDFs for the Casio module 690, each a different scan (English included). Casio fitted it in the DW-310, DW-240, and DW-260. Casio's spec sheet lists one CR2016, with 5 years of battery life and accuracy within ±15 seconds a month; the module first shipped in Jun 1987.