20 C.F.R. § 703.501
Every employer who has secured the payment of compensation as required by 33 U.S.C. 932 and by the regulations in this part may request a certificate from the district director in the compensation district in which he has operations, and for which a certificate is required by 33 U.S.C. 937 , showing that such employer has secured the payment of compensation. Only one such certificate will be issued to an employer in a compensation district, and it will be valid only during the period for which such employer has secured such payment. An employer so desiring may have photocopies of such a certificate made for use in different places within the compensation district. Two forms of such certificates have been provided by the Office, one form for use where the employer has obtained insurance generally under these regulations, and one for use where the employer has been authorized as a self-insurer.
20 C.F.R. § 703.501