According to Wikipedia, The Eco is the proposed name for the common currency that the West African Monetary Zone (WAMZ) plans to introduce in the framework of
Economic Community of West African States (ECOWAS).
After its introduction, the goal is to merge the new currency with the West African CFA franc (used by most French-speaking members of ECOWAS since 1945) at a later date. This will create a common currency for much of West Africa.
Ten criteria
For the Eco to be implemented, ten convergence criteria, set out by the West African Monetary Institute (WAMI), must be met. These criteria are divided into four primary and six secondary criteria. Up to the fiscal year 2011, only Ghana has been able to meet all the primary criteria in any single fiscal year.

The four primary criteria to be achieved by each member country are: [2]
A single-digit inflation rate at the end of each year

: A fiscal deficit of no more than 4% of the GDP
: A central bank deficit-financing of no more than 10% of the previous year's tax revenues
Gross external reserves that can give import cover for a minimum of three months.

The six secondary criteria to be achieved by each member country are: [3]
Prohibition of new domestic default payments and liquidation of existing ones.
Tax revenue should be equal to or greater than 20 percent of the GDP.

Wage bill to tax revenue equal to or less than 35 percent.
Public investment to tax revenue equal to or greater than 20 percent.

:A stable real exchange rate.

:A positive real interest rate.

History of the currency!

The goal of a common currency, first in West African Monetary Institute(WAMI)/West African Monetary Zone(WAMZ) countries [4] – The Gambia, [5] Ghana, Guinea-Conakry (which is French speaking but does not use the CFA franc), Liberia, Nigeria and Sierra Leone – and later in the whole ECOWAS area, was officially stated in December 2000 in connection with the formal launch of WAMZ.
The Eco was first planned to be introduced in 2003, but this was postponed several times, to 2005, 2010 and 2014.
At a meeting of the Convergence Council of Ministers and Governors of West Africa on 25 May 2009, the start of the currency was rescheduled to 2015 due to the international economic crisis.

[6] The December 2009 meeting also established a plan to begin work to merge the Eco with the CFA franc immediately upon the launch of the Eco; this was planned to be achieved by 2020. [7]
In 2001, the West African Monetary Institute (WAMI) was set up with headquarters in Accra ,
Ghana .

Source for more. https://yawabase..com/2019/08/what-eco-currency-have-in-common-with.html