I'm guessing you mean "before plastic/nylon dulcimer picks" were invented. Picks of many kinds have been used to play zitter family instruments for over a hundred years, both in America and in many other parts of the world. Including picks to play most of the mountain dulcimer's antecedent ancestors.
People might have used any number of materials as picks before plastic picks came along, and they may well have used them on early Appalachian dulcimers:
Wood picks (either flexible or rigid), bone, flexible shirt collar stays or corset stays, leather, heavy felt, rubber pieces, fiber or wire cords, basket-making reeds... you name it. Picks do not have to be flexible. As long as it could be thin and narrow enough to hold and target individual strings, and not cut the string, it could be used.
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