Matteo,
Social Security is sort of a retirement plan, set up during the Depression years (1930s). The number is supposed to be used ONLY for this plan, but since just about everyone has a Social Security number now - you can't get a job without it - many businesses use it as an identification number. My state (Missouri) even used it as a Driver's License number for several years! (idiots)
A few years after the plan went into effect, it was modified (through Congress, I think) to include disability benefits - and dependent benefits too, I believe (husband dies, wife can receive his retirement benefits, etc).
It is
extremely difficult to get the disability benefits, and that's usually when a lawyer comes into the picture. If the lawyer is ultimately successful, the person receives a "lump sum" (the total of what they should have been getting all along, up to that point). Generally, a lawyer will receive about 25% of the total lump sum payment as his fee. The lawyer gets nothing if he is ultimately UNsuccessful in proving the case.
Social Security is a sensitive issue with a lot of people, and is a major headache for politicians.
Anyway. That holder thing of yours was something that people could buy to protect their Social Security card from wear. Not so effective in the earth, though
hope that helps,
Nan