Hi dear candidate,
In case you do not remember your roll number to find your marksheet, you try contacting your school if they still have the records or as a last resort you can look at Digilocker or use the duplicate marksheet portals like CBSE's DADS portal but may need to pay a certain fees as your marksheet is older than 20 years.
Know complete details at:
https://school.careers360.com/boards/cbse/cbse-duplicate-marksheet-apply-status
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