We have a custom object that requires a record type to be selected.  Before the administrator created the different record types the custom table id was captured in the Sandbox. I was too late when they went to production and now I cannot figure out how to get the full ID of the custom table.  I do not need the ID of a specific record or the 3 digit prefix of the object.  I need the full ID of the custom object.

For instance the URL the works in the Sandbox contains the full table Id after the value or "ent=XXxXXXXXXXXXxxx'  This process then calls a visual force page that calls a class and prepopulates the custom object.

Example.
var TheURL = "setup/ui/recordtypeselect.jsp?ent=01I500000007Qqe&retURL=/{!Opportunity.Id}&save_new_url=%2Fapex%2FcreateProjectFromOpportunity%3Fid={!Opportunity.Id}";

Could someone please explain to me how to get the full id of the custom object?  I cannot use the 3 digit prefix of the object and cannot use the name of the custom object in place of ent=01I500000007Qqe like ent=CustomObject__c.

Thanks.