LiIo batteries and understated capacities

I’ve been buying LiIo batteries for a good while now and one thing I can for sure is that you cannot always trust stated capacities.

Just wondering….if you bought a dozen LiIo batteries (same capacity, ratings, shape, size etc) should they all be about the same weight or can it vary a lot even so?

Reason I’m asking is I was under the impression that the density of the material gave the battery most of it’s weight.
But I have seen batteries that were filled with sand to make up the difference (dirty tricks)

Other than electronic testing, is there any reasonably good way to tell from any physical characteristic if a battery is a scam (less capacity than stated)?

Buy Quality names Samsung /Sony/Etc from well known suppliers Illumination Supply
/Lion Wholesale / Etc

You can if you stick to reputable brands.

Just buy from the large well known brands and skip all the cheap crap.