Hi suzan,
The law tag only lists the percentage of each type of material based on their their weight and doesn’t provide any information about the thickness of any of the layers, the order of the layers, the quality/durability of the materials, the specifics of the innerspring in the mattress, or the design of the mattress so it isn’t possible to use the law tag to try and “match” one mattress to another one.
There is more about the different ways that one mattress can “match” another one in post #9 here but unless you can confirm that two mattresses have almost exactly the same design with the same type of materials and components that are layered in the same order, have the same layer thicknesses and firmness levels, and a functionally similar cover, there really isn’t any way to know how closely two mattresses will approximate each other for any particular person outside of your own personal testing or experience and in the case of major brand mattresses that have changed over the years you won’t be able to find out enough specific information to try and match one of their older mattresses to one of their newer ones based on specs anyway.
Your best chance of success would be to follow all the steps in the mattress shopping tutorial which includes all the basic information, steps, and guidelines that can help you make the most suitable, the most durable, and the best “value” choice that is currently available to you in your area (or online) … and will also help you know how and why to avoid the worst ones (including major brands).
Phoenix