Converting the Salesforce Pod Id to ServerUrl/Name

I found one possible solution in the source code for Workbench.

They maintain a mapping structure that includes the pod identifier:

"valuesToLabels" => array(
            "login" => array("Login: Production/Developer",""),
            "test"  => array("Login: Sandbox (test)",""),
            "prerellogin.pre" => array("Login: Pre-Release", ""),
            "na0-api" => array("NA0 (ssl)","0"),
            "na1-api" => array("NA1","3"),
            "na2-api" => array("NA2","4"),
            "na3-api" => array("NA3","5"),
            "na4-api" => array("NA4","6"),
            "na5-api" => array("NA5","7"),
            "na6-api" => array("NA6","8"),
            "na7-api" => array("NA7","A"),
            "na8-api" => array("NA8","C"),
            "na9-api" => array("NA9","E"),
            "na10-api" => array("NA10","F"),
            "na11-api" => array("NA11","G"),
            "na12-api" => array("NA12","U"),
            "na14-api" => array("NA14","d"),
            "ap0-api" => array("AP0 (ap)","1"),
            "ap1-api" => array("AP1","9"),
            "eu0-api" => array("EU0 (emea)","2"),
            "eu1-api" => array("EU1","D"),
            "eu2-api" => array("EU2","b"),
            "tapp0-api" => array("Sandbox: CS0 (tapp0)","T"),
            "cs1-api" => array("Sandbox: CS1","S"),
            "cs2-api" => array("Sandbox: CS2","R"),
            "cs3-api" => array("Sandbox: CS3","Q"),
            "cs4-api" => array("Sandbox: CS4","P"),
            "cs5-api" => array("Sandbox: CS5","O"),
            "cs6-api" => array("Sandbox: CS6","N"),
            "cs7-api" => array("Sandbox: CS7","M"),
            "cs8-api" => array("Sandbox: CS8","L"),
            "cs9-api" => array("Sandbox: CS9","K"),
            "cs10-api" => array("Sandbox: CS10","J"),
            "cs11-api" => array("Sandbox: CS11","Z"),
            "cs12-api" => array("Sandbox: CS12","V"),
            "cs13-api" => array("Sandbox: CS13","W"),
            "cs14-api" => array("Sandbox: CS14","c"),
            "cs15-api" => array("Sandbox: CS15","e"),
            "cs16-api" => array("Sandbox: CS16","f"),
            "cs17-api" => array("Sandbox: CS17","g"),
            "prerelna1.pre" => array("Pre-Release: NA1","t")
        )

Do not do this. It will break the instant your org gets migrated to a different instance, and will not work if it has been in the past. You save yourself a few keystrokes now, but you (or your replacement) will endure hours of pain as they try to figure out why the migration broke the integration.