Validity of affidavit

Hello,
I want to sell my car as scrap so I asked the scrap dealer to give me affidavit on a stamp paper. Although he gave me affiavit on stamp paper ,signed the affidavit in front of me and I took his thumb impression also along with ID proof. But he told me that there are middle men who provide them affidavit with necessary information typed and scrap dealer just sign it. So my question is that -  Is the affidavit valid if he has not bought/brought stamppaper himself

Thanks
Gaurav