Work by Chris Salter and others now identify twelve different kinds of Currency Bars – only the commonest type is illustrated here.
Salter's metallurgical analyses tell us the form of the bar demonstrates the suitability of the metal for different kinds of work. Bars with metal sockets show the metal is good for forming thin sections. Those with folded-over and welded tips demonstrate that the metal is suited to welding by a blacksmith. See: Hedges and Salter 1979, and Crew and Salter 1993 for further information.
Salter's analyses also reveal that impurities in slag inclusions point to the geographical source of the iron ore. Thus we now know the likely sources for the bars and the fact that the bars were made to demonstrate the usefulness of the metal as a raw material.
The idea that the bars were some kind of "money", as asserted in Caesar's Gallic War, is somewhat simplistic. Because they can be identified by sight as suitable ingots for blacksmithing, they likely came to have a predictable value. This predictablilty would have made them useful in commercial exchanges with other objects of known value. Thus, by facilitating exchage and possibly storing wealth, they could serve some of the functions of money. But they should not be seen as official money – they are not "coins" issued by a "ruler".
The catalogue lists the four commonest kinds of bars.
Traditionally, the earliest forms of money thought to have been used in Britain were small rings of gold and iron bars shaped like swords.
We now know the rings date from the Middle Bronze Age, ca. 1500 - 1000 B.C. At such an early time they would have functioned as jewelry or hair ornaments. Their only possible monetary function might have been as a means of storing wealth.
Caesar mentions the iron bars in his writings, placing them as late as 55 B.C. There is no agreement about the way they could have functioned as money.