Seeing as no-one has replied, let me tiptoe where angels fear to...
I understand Dublin to refer primarily to the bowl shape - kind of like half an egg. Not rounded like an Apple. The Acorn/ Zulu seems to refer to three characteristics:
1. A slightly bent stem;
2. A slim, rather tall bowl,
3. That appears to be somewhat fuller than a Dublin. I'd say a Billiard, or even an Egg in some cases.