IMO, not really. You can guess, but that would be about all that you could do. Unless you have something to compare to it is quite impossible. The IM6 from a quality lot might feel better than IM7 from an inferior lot - so many things go into the final result. If you are sure of the manufacturer, you might be able to differentiate, depending on age and other factors (e.g. G Loomis uses different colors for different grades).