Basically, the co-guitarist in the band I used to be in gave it to me because he thought it didn't work (actually it had an intermittent loose connection on the input socket which I rectified) so I got the thing for nothing. He bought it in the late 80s from Andy's Guitar Workshop in Denmark Street, London. This is a quite famous store, renowned for trading second hand instruments and gear and a regular stop for well known musicians. Apparently, this pedal was sold to the store by the roadie of Gary Moore. This is what he was told when he bought it. The pedal has a sticker on one side with 'Gary' written on it in pencil. Whether I believe it or not, well, I'm not sure, but that's the story.
I put it on eBay once. The guide price from Guitarist Magazine's Vintage Pedals roundup (even for one not used by a famous musician) is in the order of 100 - 150 GBP (so around $450 SGD). When I listed it I actually got sent a bunch of abusive messages by people thinking I was trying to con people, so I withdrew it. It's not for sale now - I like the sound it makes and use it quite a lot now.