Leon I know ISMACS doesn't show the Memphis(Sphinx) decals on a 15 but they are out there. I've seen a couple of them.
The reproduction machines aren't fakes, they were sold by Singer. What they aren't, is quality machines like we're used to. The badge, feed dog drop, modern electrical connection, tension assembly, and cheaply made cabinet are all tells of a repro. The first one I ever saw in the wild was at a Goodwill and they wanted $180 for it. When I told them it wasn't an antique machine and pointed out all the things about it that proved it, they didn't believe me.
Cari