From Wikipedia
' £sd (occasionally written Lsd) is the popular name for the pre-decimal currencies once common throughout Europe, especially in the British Isles and hence in several countries of the British Empire and subsequently the Commonwealth. The abbreviation originates from the Latin currency denominations librae, solidi, and denarii. In the United Kingdom, which was one of the last to abandon the system, these were referred to as pounds, shillings, and pence (pence being the plural of penny). When spoken it was pronounced "ell-ess-dee", or more commonly "pounds, shillings and pence".'
further in the same article
'Colloquial terms ... A sixpenny bit was a "tanner" (in Australia a "zack"), one shilling was a "bob", and a pound a "nicker" or a "quid".* The term "quid" is said to originate from the Latin phrase quid pro quo.*'
It appears the correspondent is discussing financial transactions in qsd or quid, shillings and pence ( as against the local currency of Madeira)