The essay aims to investigate an economic field of activity not much known and emphasized by the historian of Medicean Florence and Tuscany, that is leather and hide industry and trade in the second half of XVI century. The research makes use of a rich bookkeeping source, through which we can penetrate in the very core of a big firm related the Capponi family, whose highest members were international merchant-bankers and senatori of the Grand Duchy. Thanks to a gigantic ledger it’s possible to reconstruct, in detail and for a ten year period, all the business of a big tannery: principal bestowed, terms of finding and payment of raw material, cost of labor incidence, sales of semifinished products and manufactured articles, annual profit margins and so on. Moreover the register let us to discover some unexplored aspects of civil justice involvement, with his abundant evidences of fees for legal actions brought against defaulting suppliers and insolvent purchasers
