A curious experiment

Every now and then, products come by which might work - and maybe might not. Here's one to leave us all wondering.

At first this was a complete mystery; it looks well-constructed, the sewn binding is robust and the mirrored covers are a challenge to photograph but just the ticket if the camera-wielder is, by a wild and crazy coincidence, dressed in purple. It's terrific, actually. But who on earth made the darned thing?

Closer inspection yielded no clues; there's literally nothing to go on. But eventually, after some decidedly plaintive importuning, news came that this was a prototype by the curiously named Mustard. 

Tantalisingly, it really is rather good - the paper even plays fairly nicely with fountain pens. But there's no word about pricing, and it doesn't look like they even make it any more, so now the mystery becomes more a question of what the plan was in the first place. It could have been a contender...