How to check replacement battery capacity claims.

When you look for replacement Li-Ion batteries on ebay for your cell, camera or whatever you meet with various capacity claims. I have come across substandard batteries with lower than claimed capacities. A simple way to determine a replacement battery capacity is to weigh both the old original battery and the new battery. If the new battery weighs less than the old battery significantly then it is lower capacity. The capacity of the battery is proportional to the amount of Li metal in there. I have recently purchased a cellphone Li-Ion battery replacement which claimed 2000mah capacity compared to 1730mah original manufacturer battery but it weighed 14% less than original. Obviously a substandard battery with exaggerated claims.