D.C. Mun. Regs. tit. 17, r. 17-407
Licenses shall be issued for steam or other operating engineers in the classes listed.
Steam Engineer Licenses (Classes 1, 2, and 3) shall entitle the licensee to operate in any lower class except Class 7.
Operating engineer licenses shall restrict the licensee to operate in the class stated on the license.
When a license has been lost or otherwise misplaced, the owner shall present a statement properly notarized to that effect and pay a fee of five dollars ($5) for the issuance of a duplicate license.
Each license shall bear a photograph and the name and signature of the person to whom it is issued.
Each license shall be displayed in a glass frame in a prominent place in the plant where the licensee is employed; except in the case of Hoisting and Portable Operating Engineers, who are issued card-size licenses which must be carried on the person of the licensee.
All licenses shall be subject to examination by any police officer or official of the District government at all times.
D.C. Mun. Regs. tit. 17, r. 17-407