Greenback period, uncoined gold bullion, or gold coin used, not as money, but simply by weight in exchanges, played an important role, competing with the Greenbacks in various employments, particularly as bank reserves, and as secondary bank reserves, and so reducing the marginal value of the money-employment of the Greenbacks themselves. Gold bullion is not the only thing which can thus serve, however. To-day, and generally, securities with a wide market, capable of being turned quickly into cash, without loss, or capable of serving as the basis of collateral loans, up to a high percentage of their value, have a much higher value, for a given yield, than have other securities, equally safe, but less well-known and less easily saleable. The "one-house bond" (_i. e._, the bond for which only one banking house offers a ready market) must yield a great deal more to sell at a given price than the bond of equal security which is listed on the exchanges, and has a wide market. Part of this is in illustration of another function of money, the "bearer of options" function, which enables the holder to preserve his wealth, and at the same time keep options for increasing its amount when bargains appear in the market. Foreign exchange performs many of these functions of money in European countries, particularly Austria-Hungary.[127] The notion that the whole value of gold coin rests on its bullion content arises most easily in a situation where free coinage has long been practiced, and where there are no legal obstacles to the melting down of coin for other uses. Where free coinage is suspended, the peculiar services which only money can perform--or rather, the services which money has a differential advantage in performing--may easily lead to an agio for coined over uncoined metal. The mere fact that coined metal is of a definite fineness well known and attested is often of some consequence, though the attestation of well-known jewelers may give this advantage to metal bars as well, for large transactions. But for smaller transactions, nothing can easily take the place of money. A high premium on small coins, apart from redemption in standard money, may easily arise from the money-use alone. And standard coin may well attain, in greater or less degree, a premium. If it is scarce, as compared with the amount of business to be done, this premium may well be greater than if it is abundant. But that an indefinite premium is possible, or that this premium varies exactly and inversely with the quantity, I see no reason at all for supposing. If the premium be great enough, men, especially in large transactions, will make use of the uncoined metal--just as they did use gold in this country during the Greenback period. The advantages of money are not absolute. Money is simply more convenient for many purposes than other things. The possibility of a premium is limited by the possibility of substitutes. It is further limited by the fact that a