The practice of engineering, of land surveying and of geology being the function of an individual or of individuals working in concerted effort, it shall be unlawful for any firm or corporation to engage in such practice, or to offer to practice, or to assume use or advertise any title or description, including the use of the term “engineer” or “engineering” in its firm or corporate name, conveying the impression that such firm or corporation is engaged in or is offering to practice such profession, unless the directing heads and employes of such firm or corporation in responsible charge of its activities in the practice of such profession are licensed and registered in conformity with the requirements of this act, and whose name, seal and signature, along with the date of signature, shall be stamped on all plans, specifications, plats and reports issued by such firm or corporation.