L. S. D
Latin, libra (a pound); solidus (a shilling); and denurius (a penny); through the Italian lire (2 syl.), soldi, denari. If farthings are expressed the letter q (quadrans) is employed. Introduced by the Lombard merchants, from whom also we have Cr. (creditor), Dr. (debtor), bankrupt, do or ditto, etc.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on L S D from Infoplease: