MJ's patent leather line Ursula is very well done. Unlike typical patent leather, it feels/looks very soft, wrinkled, and distressed -- must-have details in authentic styles. A fake bag can be spotted easily, it looks smooth and overly shiny like plastic.
I noticed that the details are harder to capture for Moss. The pictures (you received & those shown in the listing) are not very clear so I am not too sure, but they don't seem/look as smooth (plastic looking) as the fakes that I have seen. If you have it front of you, you will definitely be able to tell whether it's fake or authentic.
Moss and Lobster were heavily discounted (went through several rounds of mark-downs) at stores a few months ago, some members were able to get similar ones for around $300USD.
Based on the tag and given measurements, the bag in the listing is Small. Just like Multipocket, the style name (BOWLER or MULTIPOCKET) refers to the Smaller size by default. If it's the bigger version, the tag says LG BOWLER or LG MULTIPOCKET.