The existence of a corporation claiming a charter under color of law cannot be collaterally attacked by persons who have dealt with it as a corporation. Such persons are estopped from denying its corporate existence. (Civil Code 1895, § 1862; Civil Code 1910, § 2226; Code 1933, § 22-714; Code 1933, § 22-5103, enacted by Ga. L. 1968, p. 565,
§ 1.)