Hello,
I have doubts on this one.
This is an earlier imperforate (Scott#17) but it is the same design.

On your example the lettering of the ONE SHILLING is raggedy & the font seems different especially the N & G
The top streamer on the mast does not seem long enough.
I cannot see the sails but there should be 10, forgeries usually have 7
There should be vertical lines on the chest - hard to determine.
Watermark I believe is a crown with a cross & 2 C's below it
The overall appearance should be more defined.