The starting point is that our financial system operates on a ledger system. The ledger is a method to record financial relationships [debt], economic transactions and act as a principal recording of accounts. Five thousand years ago the earliest form of writing on our planet, called proto-cuneiform, was invented in Mesopotamia during the Late Uruk period. Proto-cuneiform consisted of pictographs — simple drawings of the subjects of the documents — and early symbols representing those ideas, drawn or pressed into puffy clay tablets, which were then fired in a hearth or baked in the sun. Ledgers are made up of transaction and balance ledgers. Bitcoin is a mechanism to store transactions. Etherium on the other hand stores balances. Fundamental to accounting is the notion of a hierarchy between a general and sub-ledger. Sub-ledgers usually contain more detail. Using the Banking analogy we may describe the US Federal reserve as a central ledger for money and the thousands of regional & national US banks operate sub-ledgers for money.  Any transaction has two places on a ledger – one on the debit side and one on the credit side resulting in a balancing between assets and liabilities. There are certain characteristics of ledgers that are desirable including immutability, time-stamped, consistency, ownership, accuracy and descriptive. Modern day ledgers are observable via everyday payment systems. The earliest forms of payment systems were negotiable order [cheques]. The main characteristics of these payment systems enlighten the mechanical description of crypto-currency. The payee details define which ledger the transaction is being to and payer from which ledger the transaction originates. Important details include a time-stamp[date], a payee, a payer, signature and amount.