Well, from looking at the listing..
photo gallery popup with enquiry
It's definitely the Mull boat, at least externally. Comparing the interior layout to the specs on sailboatdata.com there's quite a difference. Someone's confused about the S&S label, but interesting that the layout is much 'cruisier' than that shown in the specs.
I think she'll be a pretty nice boat, looks cared for and well equipped. As with any 70s IOR design you're going to have to be sensible about sail selection and sailing angles, esp in a real breeze. Motivated seller by the looks of it too.