I have a bunch of signatures on my CBG. Johnny Winter, Jimmy Vaughn, Mac Arnold, George Thorogood, pAt mAcdonald, Bob Margolin,etc and all of them are written in Sharpie marker. Sharpies are great in that they are thick enough and can be applied to almost anything. Bad thing is that they are highly susceptible to solvents such as nitrocellulose solvents and alcohols. So when you try to cover these with some sort of varnish, they tend to fade, dissolve, or outright disappear.
A while back I bought some Tru-Oil Gunstock oil which is a great varnish/finish for CBGs. It dries fast (couple of hours) and is VERY resilient. On a whim, I tested it with a sharpie on an old cigar box and to my delight, it did not fade or disturb the signature! I applied a light coat to my prized signatured CBG and no sigs were taken off. Not even the older, faded ones!
So my suggestion to all that want to save/keep the sigs you have on your CBG, get some Birchwood-Casey Tru-Oil Gunstock Finish. You will be glad you did.
Was this on a wood box or paper-covered? I have Arlo Guthrie's signature on a paper-covered Macanudo I want to preserve.
The one I tried was a paper covered Mac Portofino Cafe box and it worked really well. I would try it on a similar box using a similar sharpie first. ALWAYS test first. I did.
YES good point from Hal. ALWAYS, Always, always test this solution on ANY box using ANY marker or ink. You mileage may vary!