The baletta found in the store rooms of the Galleria Nazionale delle Marche in Urbino is made of padded leather with four pieces of light-coloured leather, stitched together and stuffed with wool waste.
It measures 5 cm in diameter. It is a similar ball to the one that the two-year-old Duke Federico Ubaldo holds in his hand, together with a racket, in the painting attributed to Alessandro Vitali and housed in the Museo Nazionale di Palazzo Mansi in Lucca.
It may very well be that this tiny object is evidence of the little prince’s games, having escaped the general dispersal of the ducal family’s belongings. 
The stocktake of Palazzo Ducale in Urbino from 1631 reports “a small table [tavolello] that was made for his Serene Prince to play ball”.

Alessandro Vitali, Ritratto di Federico Ubaldo della Rovere, Olio su tela (cm.96x67).
Lucca, Museo Nazionale di Palazzo Mansi