There were a range of NEC video cassettes with the High Definition moniker. I’m not sure they were any different from the regular ones, but it was a good way to advertise something “different”.
The NEC stuff we get here is packaged for NEC Home Electronics Australia, so it’s probably not the real NEC “Japan” stuff.
As you can see from the design, this is merely a Teac X-1, with a stainless steel roller instead of a nylon one.
A variant is the NEC HDx, which is unfortunately plastered with labels.
The cassette inside is a little strange because the plastic used in the reels is a little more grey and opaque compared to what I’d expect from a Teac, but again, it is very much a Teac design.
It is merely another variant of the other Teac X-1 with a nylon roller. So, buy NEC here is the same as buying Teac.