For the most part, the Lotus decal was put on model 66 machines made in the UK, and the Red Eye was put on model 66 machines made in the USA. However I have seen a few Lotus decal 66's that had US serial numbers on them.
Singer switched to the side clamp right near the end of the time using the Red Eye decals (and after UK stopped using Lotus) so you'll find some Red Eye side clamp machines, but not many.
Right now I have a lotus 66 in a parlor treadle cabinet, a lotus 66 hand crank in the older style bentwood case (with ribbed sides), a Red Eye side clamp hand crank in a newer style bentwood case and a Red Eye back clamp on the shelf. I've also collected 5 different sets of back clamp attachments. It's interesting that some of the designs for the attachments I have for the back clamp - I have never seen Singer use for any other model.