I'm not aware of the cultivar name 'Piggy Back' nor yet 'Piggy Bank', Mark, but I'd hazard a guess that this will be a form of Saxifraga epiphylla , a Chinese species.
This has, according to Malcolm McGregor's book, : "oval leaf blades with an acute tip, which is thick, crisp, fleshy and hairy on the green surface as well as having a bristly margin. Undersides of the leaves have purple spots. S. epiphylla is easily distinguished by the embryonic plantlets at the base of the leaf blades. The plantlets are generally formed late in the summer or in the Autumn and, where the leaves can lie flat on the ground, they will root and the old blade rot away."
Hope this helps!
