As the comment above says we really need a little context to be 100% sure, but it's probably related to the way we use 'mark' plus a number to indicate updated versions of things (most notable for cars). But note, these are not completely different things. They are similar to, and/or based on the original. An alternative word might be 'upgrade' or 'generation'. So, the idea is that the 'mark-2 wife' is an updated, improved version of his first wife.

Chris is right - a Mark 2 escort would be the upgraded, improved version of a car, so a mark-2 wife would mean the new and improved wife! Wife number 2, or his second wife...

Thanks very much.

Hi Gloria96, Can we have a little more context? I'm confused about what you're talking about making it difficult to correct. Feel free to ask me directly www.italki.com/maddie Thanks!