And there is
a thread dealing with the mass/weight of certain pills (real) here somewhere (mostly opioids) that has come in handy for me a couple times. Would be most excellent if it was kept updated but guess we gotta be thankful for what we
do have, no?
Other than what is mentioned above by Transformer: A keen eye (or use of magnification), taste and experience with the substance
can help but is not recommended as it could be too late by the time one has a chance to get a good taste of a pill.