[mikekchar]

There is exactly one way to determine good from bad shoyu - long term natural fermentation. Good shoyu is fermented for at least 1 year. Better shoyu is fermented for 2 years. Top class shoyu is fermented for 3 or more years. It is literally that easy.

This is also shared by miso (although there are styles of miso that have a short fermentation, so it's not universal). The difference between 1 year old miso and 2 year old miso is profound.

Finally, note that high quality shoyu and miso must be fermented for integer values of years because the temperature variations are extremely important to its maturation. I've often wondered if there would be an advantage to controlling this fermentation with temperature control, but it appears not. All of the top quality shoyu and miso that I know about is made in very "rustic" environments.

Anyway, so there is no need to attach strange labelling to these products. Just do exactly the same as the Japanese do - "naturally fermented for x years". If "naturally fermented" is missing, then be suspicious. If it says "fermented for x months" then be suspicious. If it says nothing at all, then be doubly suspicious.