Masana tattalin arziki sun raba nau'o'in kudaden ƙarfe zuwa manyan nau'i biyu: ma'aunin ƙarfe guda ɗaya da ma'aunin ƙarfe biyu. Na farko shi ne inda manyan kudade suke takaituwa ga tsabar ƙarfe guda ɗaya. Dangane da na biyu, watau ma'aunin biyu, duka tsabar zinariya da ta azurfa suna wakiltar babban kuɗi. Ma'aunin ƙarfe biyu yana buƙatar kasancewar halaye guda uku.

Economists divide the types of metallic currencies in to two main types: the single metallic standard and the dual metallic standard. The first is where the main currencies are restricted to one single metallic coinage. As for the latter i.e. the dual standard, both the gold and silver coins represent the main currency. The dual metallic standard requires the existence of three qualities:

1. Tsabar zinariya dole ne ta kasance da matsayin kuɗi na doka mara iyaka (ba tare da ƙayyadadden ƙarfin siyayya ba).

1. Gold coins must have an unrestricted legal tender (no fixed purchasing power).

2. Bai kamata a sami wata takura ba wajen yin tsabar kuɗi daga zinariya da azurfa ba.

2. There should be no restrictions on minting from the bullion of both metals.

3. Dole ne a kafa ƙayyadadden farashin musaya tsakanin darajar tsabar zinariya da tsabar azurfa.

3. An official rate between the values of the gold and silver coins must be established.

Ma'aunin ƙarfe biyu yana da halin babban adadin kuɗin da yake sanyawa cikin yawo, saboda amfani da tsabar kuɗin ƙarfe a lokaci guda a matsayin manyan kuɗaɗe. Saboda haka, farashi yana ci gaba da kasancewa mai tsada, kuma hakan zai kai ga ƙaruwar samarwa. Haka kuma zai sa darajar kuɗi ta fi tsayuwa, farashi kuma ba zai iya sauyawa sosai ba, abin da yawanci kan kai ga rashin zaman lafiya na tattalin arziki. Don haka a bayyane yake cewa aiwatar da ma'aunin ƙarfe biyu ya fi ma'aunin ƙarfe ɗaya kyau.

The dual metallic standard is characterised by the huge amount of money it puts into circulation, due to the simultaneous use of the metallic coins as main currencies. Therefore, prices remain high and this would lead to an increase in production. This would also make the value of money more stable and prices would be less likely to undergo major fluctuations which usually leads to economic unrest. It is therefore clear that operating a dual metallic standard is better than the single metallic standard.