I'd say that, yes, it's lead crystal and yes, it rings nicely when tapped.
I've just looked at the page from the Stuart catalogue in Andy McConnell's Miller's 20C Glass. There seems to be quite a variation in the rings, depending on the piece.
I've got some of the smaller dessert bowls in clear crystal, and some have more pronounced stepped rings. Also only some of them have the Stuart mark, but some of the signed bowls have pronounced rings and some don't.
Could we just be talking about the natural variation of mould-blown, hand-finished pieces?
Especially since I'd guess that the base of the bowl was moulded first, the stem and foot were applied and finished off manually, and then lastly the rim was opened out and fire-polished, holding the bowl via a punty applied to the foot. The constant returning of a piece to the glory-hole could easily reduce the prominence of the decoration.
Both bowl have a worn ring around the edge of the base, and that could easily conceal any original etched maker's mark.