Automatic Item Number Creation (For article posting as a Reference for Quick Searching)
Option 1. You can use an existing node ID (NID).

Each node already has an ID and can be accessed via /node/[nid], [nid] being the ID of the node. Or you can generate a path alias by inserting &lt;?php print l('link', 'node/' . $nid); ?&gt;, $nid being the ID of the node. To retrieve NID of a current node, insert &lt;?php print $node-&gt;nid; ?&gt; into node.tpl.php.

Option 2. You can also use the combination of Automatic Nodetitles and Token module. This will allow you to automatically generate node title with the values from the Token.

Once the modules are installed, go to Structure -> Content Types, click on Edit, next to your content type. While on the Automatic title generation tab, select to Automatically generate the title and hide the title field, and in Pattern for the title, post a token from the options below; see the image below. There are many options with tokens, such as Unix timestamp (my favorite), random numbers and more.



Update:

For a truly random serial number, instead of using the Token module, I'd suggest using uniquid(); it generates a 13 character long random serial, no duplicates. This would be my choice. To do so, put this into "Pattern for the title" field, don't forget to check "Evaluate PHP in pattern":

&lt;?php echo uniqid(); ?&gt;


If you have spare time, there is also a Serial Field and Universally Unique IDentifier module, which also generate unique values.