ISA Swiss 8173

Historical ISA multifunction quartz calibre with small seconds, day, date, a 24-hour second time zone and a 12-hour alarm. Its reserve indicator displays remaining battery charge, not mechanical mainspring reserve. The official sheet specifies 25.60 mm diameter and 4.60 mm height. Swiss-made and Far East assembly versions are documented. Attribution is to the historical ISA quartz range, not a claim of manufacture by the current ISA Timepieces Swiss SA mechanical-movement company.