Used the Lake County, FL Property Appraiser's taxable value as donation value. Is a separate appraisal needed?

[Opus 17]

If you are claiming a value of more than $5000 you must have an appraisal by a qualified appraiser and the appraiser must sign a copy of form 8283, that you must mail to the IRS after e-filing.  (A financially responsible officer of the exempt organization must also sign form 8283.)   

I suppose it might suffice if the county assessor will sign your form 8283.  But I suspect they won’t.