About 35 years ago, when I had only been into collecting for a short time, I spotted one of these at Birmingham Arms Fair. No one knew what it was and I was very tempted to buy it as the price was very reasonable (about £150 as I recall). Unfortunately I had limited cash, and there were a couple of other more pressing things to buy, one of which was an Abas pistol, so I had to leave it . A few years later I researched exactly what it was, and I spent the following years kicking myself that I didn't snap it up when I had the opportunity.
There is a happy ending to this story though. After a very long wait, another one did turn up, and as at the time its identity was not generally known, I managed to buy it at still reasonable (though higher) price. So the moral is, never give up hope, but expect to have to dig a bit deeper into your pockets.