Original  Reproduction 
The first view show not much different between the original and the fake nested weight !  
...
but if you have a better look on the lid, you can find often maker and
verification marks. Sometimes this marks can help to convict a fake ! On the left you see the fine maker mark of a padlock and the mark of 2lb for the total weight of the complete nest. Have a look on the L, you can see that it sit over the decoration lines but very well placed ! On the right you see the lid of a fake. The marks show only numbers in no special order. Some on the left some on the right, some in the center.... no system. Also you can see that the strut on the lid is on part with the lid. They are never made in one part !!!!! 

If you have a look under the lid you can see the next mistake. On the left you can see the correct placed rivets from the struts on the top. On the right you see no REAL rivets. Sometimes they are wrong placed or insert by casting.... well they always insert after casting !!!!  
The
view to the inset cups helps often to convict the fake. The fake cups
rattle and do not fit good. Well, better to test this by hand.... but I am
sure, you can SEE how they rattle ;) A correct fit look like a near plan surface ! 

Here you can see one of the biggest mistakes from fakes. This mistakes base on a misunderstood from the forger. The bigger nested weights have always a reinforcement in style of rings outside the house. The forger copy them often in style of steps. The problem is, a step is only a weakening of the house. A style like a step convict always a fake !!!  
The bottom of a cup is also a good indicator for a original weight. The most cups have not the correct weight after they are made. A calibrator reduce the weigh on the bottom ( the bottom is normal the thickest part of the cup ) This calibration is often to see by some scratches.  
Also
the pill indicate often the fake, a correct pill is flat and not tall like
on the right picture. This mistake happens, if the forger make as first
the biggest cup and than down to the smallest. If he forget to make the
bottom ticker than the sides, he has to much place for the last cup.... so
it is to tall !
Well, one of this mistakes alone do not indicate always a fake, but you have to proof the weight better if you find out one of this "easy to see" mistakes. After all, you can try
to test the correct weight of a nested cup ! All examples base on a 1 lb nested weight 1 lb based on 16 oz the house weigh 8 oz, the first cup weigh 4 oz and each next cup the half of the one before. The last weight ( pill ) have the same weight like the last cup ( 4, 2, 1, 1/2 , 1/4 + 1/4 pill ) 1 lb based on 32 lot the house weigh 16 lot, the first cup weigh 8 lot and each next cup the half of the one before. The last weight ( pill ) have the same weight like the last cup ( 8, 4, 2, 1, 1/2, 1/4, 1/8 + 1/8 pill ) both systems are often to find !!! You can proof the correct weight easy ! If the set is complete, all insert cups together have to weigh the same like the house. All smaller cupe have to weigh the same like the biggest cup... so you can proof all weights down to the pill. If one cup is lost... this happens often... you have to calculate the lost weight ( as example, double the smallest cup and start than to proof the cups from small to big ) Some newer nested weights base on the metric system: 1 lb based on 30 lot the house weigh 10 lot, the first cup weigh also 10 lot and each next cup weigh 5, 2, 1, 1 lot than the smaller cups 5, 2, 2, 1 q 1 lb based on 500 gram the house weigh 250 gram, the first cup weigh 100 gram and each next cup weigh 50, 50, 20, 10, 10, 5, 2, 2, 1 gram. There exist sometimes a other division but BOTH systems are always marked with the weight, so they are also very easy to proof ! Give forgers NO chance to sell weights !
