I did not make mistake i have reexaminte images and file rename and you right quality reduction to jpeg conversion has been done on file GTR 5 with photoeshop. It normal done for bitmap photo convert for email for internet upload. however offset length decode sos confirm no other edit to him.
It appear file NSJJJJJSSS converted with windows or similar from bmp to jpeg hence loose EXIF data and no camera match if you run through JPEGsnoop it should indicate uncertain if original. This will confirm for u.