Buffalo nickels dated before 1920 are worth at least $2 and often $15 each. Then there is all the old silver coinage, silver dimes, quarters and half dollars minted before 1965... minimum values are $1.40 for old silver dimes, $3.49 per silver quarter and $6.98 for each silver half dollar. No rare dates to achieve these values, just common old silver coins.
How to Report the IRS Phone Scam. If you know you owe taxes or you think you might owe taxes, call the IRS at 1.800.829.1040. The IRS employees at that line can help you with a payment issue, if there really is such an issue.
If you have run across a problem like this, the IRS suggests you call their toll free number: 800-908-4490. They will also want you to fill out Form 14039 (PDF), which is their Identity Theft Affidavit. You may also want to look at other IRS information about identity theft on their website. Article.