I would def say that they were looking for items that can be sold quickly without trace, older machinery ect,, newer stuff has too many traceable things,, the other thing is though i,m not 100%sure on, certain fertlizers ect when treated in different ways can give somesort of a high! if you understand what i mean. bit like the plastic rubbish bins when burned the idiots breath in the fumes and get a kick from it.