This ad appeared in the July 1819 issue of La Belle Assemblee. This is a by a woman for women kind of ad.
I have found some other mentions of H. Sass as a publisher in High Holborn of various articles, which appears to be part of the advertisement for drawings and materials for fancy work. I also located in a book on Royal Academy Exhibitors notes about a Henry Sass, a painter, at the same address and a Miss Henrietta Sass, also at this address, and who also was a painter.
Henry Sass, in fact, has his own wikipedia entry that details the Sass’s Academy: Henry Sass – Wikipedia
The wikipedia mentions a transfer of the school to Francis Cary, but its evident that one of his daughters (he had nine children) was running the school for many years before the 1842 transfer to Cary.
