As per the Income Tax Act, the relevant records to support the returns of income, like the cash book, ledger, and income and expenditure statement, are expected to be retained for 9 years from the date of such filing. If the I.T. department does not ask for records prior to 9 years, it is unjust for a PF inspector to ask for records before that.
You need to produce your PF records, such as Form 5/10, 12-A, monthly challan, and 3-A, 6-A, Form 2/11, etc., with the books of accounts for a maximum of 9 years. Maybe the inspector is trying to prepone the coverage. If you are firmly convinced that the employee strength (in the case of regular/casual/contractor employees in a clubbed fashion) does not exceed 19 at any time prior to your application, you need not worry at all.
In case of any harassment, directly write to the Central Provident Fund Commissioner, marking a cc to the Regional Provident Fund Commissioner.
Such acts are mostly done by inspectors with an expectation of illegal gratitude. We are here to comply with the provisions (in genuine cases only).
Hope for the best.