Within the Treasury Account Symbol, this is used in conjunction with the main account code, the Agency Identifier represents the department, agency or establishment of the U.S. Government that is responsible for the Treasury Account Symbol.
20 PAR cans. A parabolic aluminized reflector lamp (also PARCAN light, PARcan, or simply PAR) is a type of electric lamp that is widely used in commercial, residential, and transportation illumination. Usage includes locomotive headlamps, aircraft landing lights, and residential and commercial recessed lights (cans in the United States).
Both answers above are correct. Just adding a different look. Par and R 20's can be incandescent, fluorescent and LED. The most common lamps are the 45R20 and the 50Par20's. The pars have a parabolic glass that deflects the light a little better than the R's. The Par's are halogen, burn at a little cooler color (regular incandescent is aprox 2700 kelvins and Pars burn around 3000K.) Now here's the big difference.