A Question About Stanley Gibbons Catalogue?

Can anyone tell me what means when for the value is something like cross... what means when is a horizontal line... and what means when only is an empty space? I am new with this catalogue, and a confused a bit... Thanks.

The "cross" means the stamp is not known to exist in that condition.
The "dash" means it exists (or may exist), but no market price is known.

A "blank" could mean a whole lot of things, including either of the above, or that they simply didn't bother to price it. In other words, the catalog editor chose not to "fill in the blank".

The cross... more like a dagger means it does not exist.
A horizontal line or blank means it exists but the price is unknown (probably because few examples come on the market I think)

Found this in my own SG catalogue...

+ (dagger shape) (in price column) does not exist.
- (in price column) exists, but no market price is known (a blank conveys the same meaning)

I've always wondered why they bothered to put the "-" in SG if the "blank" means the same thing. Seems like there must be some subtle difference that they are not acknowledging.

For instance, in Scott, the "-" means the item is known/reported to exist, but either catalog price is yet to be determined or there are still some verification issues. Either way, "-" in Scott means at least somebody somewhere reports/claims it does exist. So it is not the same as a "blank" in Scott.

thanks to all! so, if I come accross a stamp which is marked with any of that 3 things, I should need to expertize it more carefully?

Stanley Gibbons editor wrote :
"To take the dagger first: sometimes this is used where something clearly cannot exist, such as an unused stamp on a cover, but also where an item is not believed to exist."

"Blanks or dashes may be used for a number of reasons...
A listing may be based on an authorative source "(he gives an example noted in a Postal History book where the authors did not state if the stamp was used or unused, so neither was priced).
"Plate Flaws and varieties are usually listed on the basis of unused examples often shown in positional blocks, allowing all the necessary details to be included in the listing. Clearly, used will probably exist, but in the case of British stamps most are only priced unused..."(older stamps are not in that category so will be listed).
"Used missing colour errors are another problem as it is often not possible to be sure that they have not been deliberately or accidently created (by being subjected to prolonged sunlight). Here, there would have to be good evidence for the bonafides of the error before listing and pricing could be arranged."

"If you have a stamp which is listed but not priced in the catalogue... it is quite probable that we just don't know of its existance. Usually, it would be necessary to inspect the stamp itself, or a reputable certificate if it has one, but a good, high resolution scan may be sufficient for some items, so why not tell me about it".

Thanks for asking the editor and posting the reply, scotzm!

Of course, I'm still not sure why SG bothers to put a dash, if a blank/dash mean the same thing.