So it could be a giant fruited Ponderosa clone plus some trick of fertilization/hormones.
On the Mr Texas site there is also a photo of Panzarela lemon that is approaching this huge size.
http://members.fortunecity.com/pjsauber/Panzarella.htm
Joined: 27 Dec 2010 Posts: 231 Location: Hungary, Europe, Zone 6
Posted: Sun 04 Dec, 2011 5:59 am
I believe Nine Pound Lemon and Ponderosa are not the same. Here are few info's http://citrus.forumup.org/post-41333-citrus.html and also in the catalogue of Tintori is mentioned as different variety.
They labeled as C. Limon Nine Pounder - Olanda.
Joined: 04 Sep 2009 Posts: 276 Location: France, 40km South of Paris
Posted: Sun 04 Dec, 2011 10:52 am
Probably they are not identical, but the outside appearance and size are very similar. The photo in this thread shows also rough appearance of the rind. It looks like oni-yuzu: