Hi,
There are many, many sellers on ebay who use Bonnie Cashin's name to generate interest in their bags. Most of those sellers don't have a clue if Cashin designed it or not.
Personally, I don't know if Cashin had anything to do with the bag you asked about since it isn't a style I recognize. I have seen some of her actual "authenticated" bags sell for big bucks and they were in excellent condition.
The only way to authenticate it as a "Cashin design" is to submit photos to BonnieCashinFoundation dot org. For $20 they will tell you if it is her design.
I would only buy a bag if I liked it and wanted to use it. The seller of that bag needs more photos of the "wear and tear" because some wear and tear can't be "fixed".
Just my opinion.