EXTREMELY RARE 

WEIGHTED PLASTIC NUMBERS 

Numbers are the same height but weigh proportionately to their identity.

Math STEM Educational Manipulative

for Balance Scale -- No scale included. Internet has many ideas for making a balance scale for kids. One is as simple as using a hanger, string, and paper cups. 

Numbers are not magnetic. One picture shows the reverse sides.

The only numbers I found like these are in a Frogotter Box used in England in conjunction with the English National Curriculum.