The markings on the bottom of the drums is as follows (there are no other markings other than the contents labels which are paper and have been removed):
2 (surrounded by circulating arrows; probably indicating the nature of the recycling process to be used with these drums) HDPE (high density polyethylene) 5-10HLM1 M4766 8/95 (date of manufacture) UN/1H1W/Y1.9/190/95 (drum specification) USA/+AA0821 (drum specification) 2.2MM
The drum material is believed to be polyethylene (black) and the drum style is similar to Delcon closed-head type 74101 55 gallon containers. Drums are blow molded. Closed head drum has one 2-inch NPT plug and one 2-inch buttress and accommodates standard filling and emptying devices. Designed to be used with foods, corrosives, acids, cleaners, hazardouste waste, pharmaceuticals, photo chemicals, class B poisons, bleaching chemicals, but not for fuels or oils.
Take me back to the International Aerial Robotics Competition rules.