Need Help Identifying Bahamas 6 Pence

Please help me identify this stamp.
Back photo is in watermark fluid.
Is the JG an expertizer's mark?
Thanks

More likely a collector's mark.

It's an 1862 perf 13,but your stamp was used for revenue purposes.
(ink cross).

https://www.revrevd.com/bahamas.html

Well spotted ! I missed it.

That's interesting perf12, thanks for the link. What impact does that usually have on stamp valuation? I don't know much about this stuff and am sure that I could learn a ton when the forums search is working again. Google just doesn't cut it.
Regards,
H2oya

Stamps from the British Empire were commonly used for fiscal purposes, hence the "postage and revenue" text that appears on many later issues. Some high denomination stamps were principally designed for fiscal use. A label used for fiscal purposes ceases to be a postage stamp, and the values listed in Gibbons's catalogues do not, therefore, apply. Maybe a tenth of catalogue value (bearing in mind also that catalogue values and real-world selling prices are usually some distance apart) for most stamps.

The watermark you see is from the edge of the sheet.