I read the title and thought "Why would Arno pick a gold-plated watch as the perfect dress watch when he has the solid gold version?". My question was answered when I opened the post and saw that it was indeed your 2456 you meant - 2448 is the gold-plated Carrera 12, 2456 is the reference for the solid gold one.

It's a bit of an odd reference because it continues from a pre-Carrera:

over into the Carrera line itself. Unfortunately, it's only ever a footnote in the brochures (i.e. oh yes, this is also available in 18K):

That one nicely shows the price relative to a 2447 too. They do seem to be quite rare, I have only seen a handful in years of collecting, whereas the 2448 does seem to be relatively common.

As to ultimate Heuer dress watch, well it's up there, but there are some others for consideration: 1158 (of course!), any triple calendar and the white Cortina deserve mentions too. Panda and inverse panda first generation Carreras too.