...Bustermonty, could be the reason your rare Texaco No Smoking sign didn't move is that people are far more likely to buy unrestored items...that way, they know what the 'real' sign looks like...
...in a weird way, kinda like a guy wanting to see his girlfriend without all of the makeup, before he proposes...

...now, before everyone gets on my case for not being a rah-rah cheerleader, I'm just stating my opinion, and my view of the market...seems like a couple of rare globes that had been extensively restored were snubbed by the High Rollers at a well-publicized auction not too long ago - not because they weren't rare or desirable globes, but because they were extensively restored...I do remember one of the globes was a Jumbo Gas with the elephant...
...while the considerable $$ that goes into a given pump restoration can generally be recouped by the seller if the buyer is satisfied with (1) the gasoline brand/paint scheme and (2) the quality of the job, I just don't see the same trend with restored signs or globes...seems like the prices realized for a restored sign/globe aren't much more than the unrestored sign/globe would have brought...and nowhere near what a clean, unrestored sign/globe would bring...
...I did speak with the Van Kannel brothers (nice guys, by the way) at Columbus in 2004, and took photos of a Clean, Clear, Golden Texaco pump sign they had done, as well as a shot of the 'before' photo they had taped to the back of the sign...I am pretty sure they fill, repaint and clear-coat; definitely a 'non-porcelain' process...I will post the photos tomorrow sometime...
...basically, a lot of collectors just won't touch a heavily-restored sign...but, as the number of high-grade unrestored signs continues to dwindle, perhaps the market for such pieces will improve...only time will tell...but we owe it to the 'newbies' - the future of our beloved hobby - to give them as many facts as possible and let them make as informed an decision as possible...