It is the largest collection of medals to be offered at auction since the Henry Oppenheimer sale at Christie's in 1936 and will be dispersed across three sales. This particular medal will probably appear when the first tranche of the collection goes under the hammer in May.
Depicting the 21-year-old daughter of the Marquis of Mantua, the medal was made by the early Renaissance artist and medallist Antonio Pisano (c.1395-1455), known as Pisanello, and dates from 1447.
Pisanello is regarded as the most important commemorative portrait medallist in the first half of the 15th century, and while Cecilia Gonzaga is depicted in profile on the obverse, on the reverse she is shown de-robed in a moonlit landscape, representing the figure of Innocence who, as a virgin, is able to tame the Unicorn.
It is estimated to make in excess of £65,000.
The collection, formed primarily in the 1960s and 1970s, has barely been seen since. Michael Hall gave most of his British medals to the Los Angeles County Museum some years ago, although some important pieces were retained and will be offered in Baldwin's sales.
The sales will include a large number of early Italian medals as well as others from France, Germany, the Holy Roman Empire and the Netherlands. There is also an extensive group of Papal medals.
