Except on a ground for which application to cancel may be filed at any time under subdivision (4) of section 35-11g and except to the extent, if any, to which the use of a mark infringes a mark registered or published by the United States Patent and Trademark Office prior to the date of registration pursuant to this chapter the right of the registrant pursuant to this chapter to use such registered mark in commerce within Connecticut for the goods or services on or in connection with which such registered mark has been in continuous use for five consecutive years subsequent to the date of such registration in Connecticut and is still in use in commerce, shall be incontestable; provided (1) there has been no final decision adverse to the registrant’s claim of ownership of such mark for such goods or services, or to the registrant’s right to register the same or to keep the same on the register; and (2) there is no proceeding involving said rights pending in the United States Patent and Trademark Office or in a court and not finally disposed of; and (3) no incontestable right shall be acquired in a mark which is the common descriptive name of any article or substance, patented or otherwise.