William Holland (1809-83) was a maker of stained glass and other decorative items based in Warwick. He was later joined by his sons and nephew, Frank Holt (1843-1928), who after William’s death carried on the business as F Holt & Co.
William Holland on Wikipedia
Stained Glass Marks and Monograms complied by Joyce Little and edited by Angela Goedicke & Margaret Washbourn. (Published by the National Association of Decorative and Fine Art Societies, now The Arts Society, 2002)