One possessing a license, commission, or certificate of competency issued by the proper authority and usually after an examination. U. S. v. Forbes, 25 Fed. Cas. 1141; Petterson v. State (Tex. Cr. App.) 58 S. W. 100; Dean v. Healy, 06 Ga. 503; State v. Follett, 33 La. Ann. 228.