The sources that have been calendared here are kept in the family archive in the palace on Lake Maggiore, Piedmont: Archivio Borromei Isola Bella, henceforward ABIB.
The sources that have been calendared here are kept in the family archive on the Lake Maggiore, Piedmont: Archivio Borromei Isola Bella, henceforward ABIB. The archive holds documents from the fifteenth century onwards and has been reunited in the current location since the 1950s-60s after a decade in which they had been dispersed in various family estates during the second world war (the RAF bombing of 1943 damaged the palace in Milan, the archive’s original location, and destroyed some of the folders).
The archive contains dozens of account books, including a series of the fifteenth century. In particular, there are eight surviving ledgers (Libri di Debitori e Creditori, Debtors and Creditors) for Borromei companies across Europe: Mastri n. 6 and 6/2 for Giovanni Borromei & Partners of Milan (1427, 1428); n. 7 for Filippo Borromei & Partners of London (1436-39), which will be here referred to as BLon; n. 8 for Filippo Borromei & Partners of Bruges (1438), which will be referred to as BBru; n. 9, 10, 11 and 12 for Filippo Borromei & Partners of Milan (1445, 1446, 1451-52, 1453-55). Moreover, four ledgers (n. 1-4) concern the activity of Vitaliano Borromei as a ducal treasurer (1421, 1424, 1427, 1428).
For this project we calendared n. 7 (London, for the years 1436-38) and n. 8 (Bruges, 1438), amounting to c. 23,000 records.
Both ledgers include the index of account holders, arranged alphabetically (in London the index only covers the years 1436-38): as customary, the alphabetical order is by first name. The sides of the pages containing the index have been cut back to produce a thumb-nail finding aid (see Image 1 at the bottom of the page).
It is important to point out the difference between a page and a folio in a ledger kept using the double entry method of book-keeping (see section on Accounting). A page is simply one sheet, in this case of paper, with recto and verso side, so that when a book is open we would find the verso of one page on the left and the recto of the following page on the right. A folio in a double-entry account consists of the left-hand page, on which the debit or dare entries are made, with the folio number given in arabic numerals, with the right-hand facing page for the avere or credit entries, and the (same) folio number in roman numerals (see Image 2a and Image 2b at the bottom of the page).
Each folio contains a variable number of accounts, up to twelve in London (f. 49), where the accountant’s handwriting is tinier and messier (see Image 3 at the bottom of the page)
The ledger was the third in a series which began with the libro rosso (1436) and the libro morello (1437). This is the libro verde and its two successors were the libro azzurro (1439) and the libro bianco (1440). Alas, no other book has survived. Each was probably the same size as this ledger which is a large, bound book of 396 pages, recto and verso, of which about twenty (ff. 1-2, 220-29, 255-63, 389-90) are blank; ff. 3-219 and 230-54 contain the company’s own accounts, those of clients who were resident in Bruges and the loro accounts of merchants resident abroad; ff. 264-351 and 391-96 were for conti nostri, ff. 352-88 for merchandises, expenses and losses (for more details on the loro and nostri accounts, see the section on Accounting).
The leaves measure 400 by 320 mm., or approximately the size of a modern A3 sheet of paper. The book itself was bought for the bank by, interestingly enough, Alessandro Borromei and Antonio di Francesco & Partners of Bruges, members of the Venetian branch of the family, along with a journal or daybook and two other smaller books, all for £1 2s flemish (BBru ff. 51, 363, 20 May 1436). On the recto side of the first leaf of the Bruges ledger there is this image, which shows the company’s trademark (see Image 4 at the bottom of the page).
This book, of 474 pages (some of which are blank), includes four ledgers of four consecutive years, from the year of foundation (1436) to 1439: ledger 1436 (ff. 4-50), 1437 (ff. 53-147), 1438 (ff. 150-266), 1439 (ff. 270-448). The ledger for 1439 has not been calendared here (see Image 5 at the bottom of the page). The accounts that were still open at the end of 1439 were carried forward to the libro nero of 1440, which unfortunately did not survive.
The opening page of the London ledger has the same trademark as Bruges (as the company of London was a branch of that in Bruges), preceded by exhortations to God the Father, God the Son and God the Holy Ghost, the Virgin Mary, St Mark, St Peter, St John, St Ambrose and All the Saints in Heaven.
The London branch paid £1 14s sterling for its books which were bought for them in Bruges on 9 March 1436 by the main company (BLon f. 17).