04.21.1851 - Letter from Mantua to Pavia franked for 30 cents by means of a pair of 15 cent. I type. with sheet edge on the left, both values present the variety '' 5 similar to a 3 '' n.3o. This letter appears to be the only known case of a multiple of this variety, for Sottoriva citing his certificate: '' To be numbered, rightfully, among the most important and valuable letters of the sector ''. (A+) (Cert. Sorani, Cert. Sottoriva)