The British numismatist Philip Grierson disagrees with the "star" etymology, as the stars appeared on Norman pennies only for the single three-year issue from 1077–1080 (the Normans changed coin designs every three years). Grierson's proposed alternative is that "sterling" derives from "ster" meaning "strong" or "stout", by analogy with the Byzantine solidus, originally known as the "solidus aureus" meaning "solid gold" or "reliable gold". In support of this he cites the fact that one of the first acts of the Normans was to restore the coinage to the consistent weight and purity it had in the days of Offa, King of Mercia. This would have been perceived as a contrast to the progressive debasement of the intervening 200 years, and would therefore be a likely source for a nickname.