If you take a look at Leapers pages at studiopottery.com there are several examples of his mark and no two are alike, so I wouldn't be too concerned about that, but Lustrousstone has a good point. I didn't notice the pinkness of the clay which, now I've seen it, does set faint alarm bells ringing, but then again, are Leaper pieces really valuable enough to be worth copying? I think that you have to decide whether it's worth taking a chance at ?15-20, though if you have doubts now then you might be best leaving it alone.