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Brass or bronze? Got me again

I see on the U.S. Mint’s list of products that are coming soon that the annual uncirculated coin set now has an Oct. 1 sales date. This contains an uncirculated example of every denomination and design struck at both the Denver and Philadelphia mints.

Sales of the uncirculated coin set were postponed when the Mint had a problem with toning on the new copper-alloy cents, or I should write the old copper alloy cents.

The law authorizing the four designs for the 2009 Lincoln cents also requires that they be minted for collector sets in the alloy that was used in 1909, which was 95 percent copper, three percent zinc and two percent tin.

It is perhaps not surprising that a problem of this kind would have occurred. The Mint is out of practice with such an alloy. Collectors know how prone to toning and spotting cents are. That is why they are usually the first coins looked at in sets to see how well preserved the overall uncirculated or proof set is.

In this blog I did not call the alloy bronze as I did in August. Alan Herbert, the Answerman, e-mailed me about that.

He wrote, “95 percent copper and both tin and zinc can go either way. If the majority is tin, then it’s bronze, but if the zinc makes up more than 2.5 percent, then it’s brass.”

By that definition, the cents will be brass. This is a good example of why Alan is the Answerman who writes the weekly Coin Clinic question and answer column in Numismatic News.

So, will you be a buyer of the uncirculated coin set containing brass cents?