the 8,12 16,20 refer to the diameter. If you have a measuring instrument such as a veneer caliper etc, you can just measure.
As to the quality of the steel eg maleability etc, last time i checked at Devki, they did not chemically analyse since they used scrap metal. Associated Steel are more detailed . They should be in a capacity to offer detailed chemical analysis of their steel eg carbon content, iron content etc.
With the numerous building collapse, i am hoping that Kenya bureau of standards will move a step further and enfroce steel standards not just in terms of diameter, but to include chemical analysis content eg % of carbon, iron ,manganese , how malleable the steel is etc. KBS should set the standards in conjunction with Engineers association of Kenya.
As Iron Sharpens Iron, So one Man Sharpens Another.