Version Control of a Content Type
The Features module is designed for this sort of database content to code version control. You could create your content type and export it as a Feature. That feature could then be version controlled like any other source code (using Git, SVN, etc).

If you just wanted to duplicate content types, the CCK module in Drupal 6 has a Content Copy sub-module that allows just that. In Drupal 7, I'm not sure if this is built into core. I would accomplish this task using Features.