Currency
Everywhere on Tear, money is valued according to the silver standard, and for the vast majority of the population money changes hands as cash made from standard coins and ingots. Coins and ingots are not usually minted by states, but by the banks who hold vast reserves of cash along with other valuable commodities. Sometimes a large, wealthy state will mint its own currency, but this is normally done out of pride than as a function of any real economic need.
While the vast majority of individuals exchange money as cash, the majority of money is not exchanged by individuals, but by banks, states and other large organizations. When such exchanges become central to the economy, other forms of currency arise to facilitate trade.
Abstract Currencies
In places where the rule of law is consistent and well established, people can begin to trust the promise of large scale institutions such as governments, armies, companies and banks. Often, in more sophisticated societies, the lines between these things can become blurred. Regardless, such institutions have a vested interest in stability and continuity and also tend to have a need to exchange large sums of money on a regular basis. This is where abstract currencies, and the professionals who enable them, come into play.
An abstract currency is any financial instrument whose value is based on trust in the institution that issues it. Essentially, these are documents; cheques, promissory notes, deeds, bonds, or other written instruments that are signed and sealed by authorized agents, and which define the terms of their own value. In most cases, such instruments are entirely custom, but in some cases, where large, sophisticated, stable, and trustworthy institutions persist for long enough, such instruments can become formulary.
Alternative Financial Instruments
Following are several different types of financial instrument that may be available in certain contexts.
Bank Note
A bank note is a form of paper currency which can be issued by a bank or other organization that holds a reserve of capital in order to facilitate the transport of currency. Such notes are issued in fixed denominations (usually between $100 and $10,000), and are elaborately printed and sealed so as to protect against forgery. They typically also have an expiry date for the same reason. While bank notes are principally intended to support and facilitate merchant activity between cities where the issuing bank has offices (and vaults) they are not registered, and therefore can be freely traded as cash - though this is not without risk as forgery attempts are common and the banks themselves are quite adept at detecting forgery. You certainly don't want to be stuck holding bank notes - even forged ones - when they expire.
Bill of Exchange
A Bill of Exchange is essentially the same as a Promissory Note except that it is typically made between organizations or governments and covers large or complex transactions. A Bill of Exchange is always custom authored for a specific transaction or group of transactions. It will involve accountants, lawyers, and officials from all sides of the transaction, typically negotiating for days or weeks before the final terms of the Bill are agreed, signed and sealed by all authorized parties. A Bill of Exchange is probbaly not forgable, and its loss, destruction or tampering with would generally lead to all invested parties agreeing to simply renounce the Bill and draft a new one. Players are not likely to have any reason to concern themselves with such financial documents... but you never know.
Bond
A bond is a document typically issued by a government or large organization that promises to make scheduled payments to the holder over time, before returning the total amount of the bond at some specified future date. Bonds are usually issued in order to finance large infrastructure or development projects, or to raise capital for wars. Bonds typically pay between 3% to 10% of their total value per year, before returning their initial value at the end of their term (usually also 3-10 years). A 5 year, $5000 bond at 5% pays $250 per year for five years, then at the end of the 5 years, returns the original $5000. Bonds are typically of interest to the middle classes, and so are usually issued in values ranging from $1000 to $10,000. Bonds may or may not be registered, and unregistered bonds can be freely transacted, making them a target for theives.
Cheque
A cheque is a type of promissory note that requires a bank as an intermediary. A person or organization who has an account with a bank can write a cheque that orders the bank to relinquish funds from their account to the bearer of the cheque. The bank determines the security of the system; usually requiring the cheque be signed and/or sealed in a manner previously registered with the bank. In general, the amount of money that a bank will transact via cheque is fairly small (less than $10,000) unless the bearer of the cheque also has an account with the bank, in which case transactions can be as large as the account being drawn on - and sometimes even larger, depending on the relationship between the bank and writer of the cheque and the bank's comfort level with risk.
Deed
A deed is a document that represents ownership of a piece of real property; usually land, a building, a ship, or some other large or immovable asset. A deed is registered, meaning that some authority - usually a governmental organization such as a city or state - tracks ownership of the asset, and the holding of the deed itself is mostly a formality used in the process of transferring ownership. As a general rule, all extant real property within the domain of control of a government will have ownership registered by deed. A deed can have a theoretically unlimited value.
Proxy Currency
Proxy currencies are substitute currencies usually issued within a tightly defined region or for use exclusively within an organization such as an army. Proxy currencies typically consist of simply printed notes, beads, or small tin, iron or copper coins with inflated values. Proxy currencies allow financial transactions within their defined domain, and free the organization or region and its members or residents from many of the risks and troubles of carrying or transporting real currency. For example, an army may pay its soldiers in a proxy currency, allowing them to buy, sell and trade goods between themselves or within their encampment or fort, while at the same time, creating disincentives for petty theft, and also keeping the real capital reserve of the army centralized for protection. Soldiers mustering out or taking leave can freely exchange their proxy currency for real currency through the administration. Some cities may issue proxy currencies, particularly if they are suspectible to external threat. Such cities may even demand travellers or merchants reliquish real currency in exchange for proxy currency on entry, with a promise to exchange it back on departure - a promise that can be revoked in the event of conflict or turmoil. A proxy currency is generally considered to be worthless outside its prescribed domain, though sometimes black or grey markets may deal in a proxy currency, particularly if the use of the proxy currency is being heavily controlled or imposed on people.
Promissory Note
A promissory note is a simply a letter written by one party, promising to pay another party. The note can be for a fixed amount at a fixed deadline, or it can define rates or other terms, depending on the complexity of the note. In most cases, such a note passed between individuals or small businesses who trust one another can be nothing more than an 'IOU' notice. In more complex cases, or cases where the parties may not have an existing relationship, officials such as lawyers, notaries, tax collectors, or bankers can be paid a small fee to witness the signing and sealing of a promissory note, affording certain legal recourse to either side in the event of default.