It's a badge-engineering job - fairly sure it's made by the very capable Chinese company Medeli - you'll find identical models badged for Alesis, G4M, Johnny Brook etc. etc. Like you, I've owned a used one which came and went for beer money. Oddly enough I found it more playable than the Yamaha equivalents. Good fun to have and useful for reminding yourself how to play the riffs you've forgotten! Not really suitable for anything other than home use (the sounds are unsurprisingly old-school - low-res and not very expressive) although some players use them as an add-on to a larger e-kit to add percussion effects rather than allocating full-sized pads to cowbells etc. Enjoy it!
I saw one used on marketplace locally, and was curious if it might be a decent way to add electronic effects to my main kit...so I'll be curious to follow, and hope that folks with experience using it chime in.
(I know there are models more appropriate z etc. the point was to be able to do it on a budget, if its even remotely close)
Keef: Y'welcome. It pays to be aware of this in general. Pretty much anything that isn't Roland, Yamaha or one of the boutique manufacturers will have come from a small handful of Chinese companies. Medeli is one, Awowo is another (http://www.awowo.com) - worth looking at their websites for a bunch of 'You mean that's one of those?!' moments. Which isn't to say the stuff is bad, by any means, just that there's not point in paying for a logo.