A penny a day - The coin here referred to was a Roman coin, equal in value, at different periods, to 15 cents or 17 cents (7 1/2 d. to 8 1/2 d.) (circa 1880’s). The original denotes the Roman denarius δηνάριον dēnarion, a silver coin, which was originally equivalent to ten ases (a brass Roman coin), from which it gets its name. The consular denarius bore on one side a head of Rome, and an X or a star, to denote the value in ases, and a chariot with either two or four horses. At a later period the casts of different deities were on the obverse, and these were finally superseded by the heads of the Caesars. Many specimens of this coin have been preserved.
It was probably at that time the price of a day’s labor. See Tobit 5:14. This was the common wages of a Roman soldier. In England, before the discovery of the mines of gold and silver in South America, and consequently before money was plenty, the price of labor was about in proportion. In 1351 the price of labor was regulated by law, and was a penny a day; but provisions were of course proportionally cheap, and the avails of a man’s labor in articles of food were nearly as much as they are now.