Hello Angie,
Here's a bit more on GGJ.
If you search Google Books for
"Johnson, George Gibson"
you will pick up freely-downloadable The Mercantile Navy List 1861 (which has information to 31 December 1860), where you will find that he got his Ordinary Master Certificate #11051 in Sunderland, but that it had already been cancelled. Either he had already been reported dead or he had lost it at a BoT (Board of Trade) enquiry for poor seamanship or intoxication or whatever.
The pages of interest are:
Book page 78 which by Google's pagination is page 85
Book page 172 " " " " " " " " page 179
Book page 208 " " " " " " " " page 215
If you'd like to PM me with your list of Gibson mariner names, I will have a look in Keys for you when I'm at it again.
Cheers,
Westoe