I'm going to try to not be too harsh here, and I'll probably fail miserably....
The 67 was a dealer package. MG had ads touting it, sent out a bunch of kits, and dealers could add it as they saw fit. Much of the Special Edition stuff never was fitted (like the fender-mount rear-view mirror) because the cars already had mirrors and the dealer would've had to fill holes and such.
Anyway, dealers took what they felt like out of the box, slapped it on, and sent it out the door.
Does this mean SEs aren't spiffy? No, they are, just as any B with cool period options is.
But anyone who says that X number of SEs were made is just wrong in the head. Because of how they were put together, there's no way of knowing how many were made. I do think, though, there's been some effort to track how many are still around.
Would I like to have an SE? Sure. But I love GTs, anyway. Would I pay a premium for one? No. Not more than a couple hundred bucks, maybe, and only then if it had options I really cared about (like overdrive).