By the time Mr. Toure died in an American hospital late last month while having heart surgery, there were many who, remembering his comment to General de Gaulle, questioned whether Guinea had been living in liberty. Its poverty, however, was beyond dispute. Guinea's external public debt is estimated at $1.5 billion and per capita income is under $300 a year.

Country's Potential Cited

Nevertheless, as Ambassador James D. Rosenthal of the United States said, ''This country really has potential.'' Within its borders are about a third of the world's high- grade bauxite, as well as vast untapped reserves of gold, diamonds, iron ore and magnesium.

Most of western Africa's great rivers find their source in Guinea's mountains, and the drought that has afflicted so much of the African landscape has touched very little of Guinea's fertile farm and pasture lands. The Atlantic waters off the Guinean coast teem with marine life.

But economists and business people here caution that developing that potential will not be easy. For one thing, a quarter of a century of economic stagnation has left its mark. The entire country has only 652 miles of paved roads, for example, and only small amounts of investment capital and skilled personnel.

And the country's new military leaders, who took over before the ruling Politburo could appoint a successor to Mr. Toure, evidently have a lot to learn about the economic philosophy they say they want to adopt. Following the coup, representatives of the ruling military committee showed up at several Western embassies asking for books on Western economic and political systems.

Currency Overhaul Suggested

The Government still has much to do to make the economic environment more habitable for foreign businesses and local entrepreneurs. Western economists recommend that price controls, particularly on agricultural produce, be allowed to rise to market levels, and that Guinea's nonconvertible and extravagantly overvalued currency be overhauled.

But it is not yet clear what economic measures may be taken.

And one American businessman here noted that coups - no matter what the justifications or intentions of those who stage them - tend to discourage foreign investment. ''Though I'll tell you one thing,'' he added. ''I'm glad investors won't have to see the words 'Peoples Revolutionary Republic of Guinea' on my official documents anymore.''

The new regime has shortened the country's name to the Republic of Guinea.