I’ve discovered that the British Newspaper Archive online service has no coverage of The Sentinel from 30th December 1881 to 1st January 1889. The microfilm apparently has no such gap, as Stoke-on-Trent City Archives states they keep… “Staffordshire Sentinel, later Evening Sentinel, now Sentinel, from 1854, on microfilm. Staffordshire Advertiser, 1795-1973, on microfilm.” I’d suspect that the British Newspaper Archive’s digitisation contractor accidentally skipped a decade-sized block of the microfilm boxes, when building the online archive.