Davey, just watch out for a blacked-out s/n on the label and a barcode sticker there or over the similarly defaced s/n on back of headstock.
Those are signs of an instrument that went through a refurbishing outfit, MIRC, who liquidated Guild inventory for Fender at close of Corona. Those instruments were dumped on the market without warranty and are probably the biggest source of Corona's poor reputation and generally lower values on the market.
A lot of those instruments actually appear to have had no problems (I think RetroRockers' F50 is one of those), but because of the liquidation price Fender did not offer warranty, and part MIRC's job was to ensure those were adequately identified.
Even the ones
with problems were in fact professionally refurbished by them.
Just watch out for sellers asking as much for an MIRC as a "first", it'll bite you harder if you ever go to sell it.
I have a "factory first" Corona D40 and honestly when I bought it and got it home I was a little surprised at the sound.
Given their reputation I expected it to be louder than my D25.
But fit and construction were every bit as good as the 2 Westerlys and finish was actually the best of the bunch.
Anyway Coronas weren't even getting much respect
here around 2007 when I first started lurking.
As I kept informal mental tabs on first-time buyer response, Coronas seemed to have the highest rate of "Underwhelmed" new owners, compared to the other factories, even then it seemed like it was only about 1 out of 6 or so.
In the meantime I noticed my D40 was slowly "finding its voice"
Then a couple of years back I saw a comment from ex-Fender CEO Larry Thomas (maybe it was his son, I've never been able to find the article again) in an interview, that his opinion was that guitars hit a "sweet spot" between 10-15 years of age, and I thought to myself "By golly, my D40's proof of that" .
Coronas ('02-'04) are now hitting that 10-15 year old sweet spot, and in the last couple of years new owner appreciation of Coronas has hit virtually 100%.
There's also a great article by former member here Jay Pilzer, outlining some of the changes that occurred in Corona that in his opinion did lower the quality, but I think time has vindicated Corona Guilds at last:
http://www.vintageguitar.com/21567/guild-in-the-post-fender-era/