In the Dresden Files books, Cold Iron is just Iron, and things made mostly of Iron count as Cold Iron.

Steel is an alloy made out of Iron and Carbon. So I did some research as to how much of steel is actually iron and I found that the carbon content of steel is between 0.002% and 2.1% by weight. Essentially, anything that is made out of steel is somewhere around 98%-99% iron and in my opinion counts as Cold Iron for game purposes. This is why the "Cold Iron" catch is +2 or +3 (depending on the amount of powers connected to the Catch), because "Cold Iron" is pretty plentiful. Basically just about any sword or knife made from methods as far back as archaic blacksmithing up to and including modern manufacturing will count for satisfying the Cold Iron Catch.

I suppose you could run into an issue with Stainless Steel as it contains 10% chromium, but I'd personally rule that Stainless Steel which is around 88% iron would still work for satisfying the Catch.

What is Cold Iron actually?
I noticed a mail is hanging in the mailq, so my question is if that is backscatter.

The mail in question:

 Jul  1 10:38:48 a1a postfix/qmgr[30971]: F2C95230470: from=&lt;compromiseh42@ebok.upc.pl&gt;,size=125817,
 nrcpt=1 (queue active)
 Jul  1 10:38:53 a1a amavis[24301]: (24301-10) Blocked BANNED (.exe,.exe-ms,dokument
 0503279005.xml.exe), ORIGINATING LOCAL [197.254.27.150] [219.69.130.6] &lt;compromiseh42@ebok.upc.pl&gt; 
 -&gt; &lt;foerster@domain.com&gt;, quarantine: t/banned-tdxHoTNjn7FG, Message-ID: 
 &lt;7316761242.25598.116038936739@lmxmxtcv.ftirrejnsjg.su&gt;, mail_id: tdxHoTNjn7FG, Hits: -, size: 
 125817, 4642 ms


Now postfix is trying to connect to ebok.upc.pl and the connection gets refused.

 Jul  1 10:47:14 a1a postfix/smtp[23733]: connect to ebok.upc.pl[81.18.192.65]:25: Connection refused

 Jul  1 10:47:14 a1a postfix/smtp[23733]: 4D1BA2304EF: to=&lt;compromiseh42@ebok.upc.pl&gt;, 
 relay=none, delay=501, delays=501/0.02/0.03/0, dsn=4.4.1, status=deferred (connect to 
 ebok.upc.pl[81.18.192.65]:25: Connection refused)


and it keeps trying to connect.
