Direct answer
397/SR726SW and 396/SR726W are both 7.9 × 2.6 mm silver-oxide cells. Their physical dimensions match, but the Murata table preserves separate SW and W drain classes.
Both are 7.9 mm in diameter; heights are 2.6 mm and 2.6 mm. Both are 7.9 × 2.6 mm silver oxide / zinc cells at 1.55 V nominal, but their drain designations differ (SW: low-drain profile versus W: higher-drain profile). Preserve the device-specified class.
Do not infer acceptability from fit alone. The device maker’s complete code and current instructions remain authoritative.