There are two...
The Celestion G12 Century Vintage, which uses the suspension,
VC, spider, cone and dust cap from the Vintage 30 but has
a neodymium motor uint. I wouldn't say it sounds like a JBL,
though - it sounds like a Vintage 30. Here's the dope-sheet:
http://celestion.com/product/14/g12_century_vintage/
The other is (was?) the Celestion G12 Century, but I think
they may not be producing it anymore; I can't find it on their
site nor in my current distributor catalog/price list. This
one had less coloration and was rated at more power -
80W vs. 60W. I may have a couple of these, but only
in 16 ohms. As I recall, they were about $100 more than
the Vintage model.
LV