Antigua Scott#1, But With Vertical Lines Watermark

Hi all!
I came across another oddity today that I am having a hard time identifying.
It looks like Antigua Sc#1 or Sc#4, but the watermark is a series of vertical lines.
Any help in identifying this stamp is appreciated...
Regards,
Mick

Opinion:
(Not an expert)
Can you offer the perforation guage, please?
In the absence of a clear Watermark, we may conclude it is unwatermarked
however, using Murphy's rule, being the stamp of any lesser value,
then it may be the later print.

Not seen your example prior.

Perforation is 15x15.
5 vertical ines in the watermark, covering entire stamp...

Thanks, be back to you.
I am of the opinion, the lines are from the design on the front, not a watermark, have you placed the stamp in a watermark medium at all?
albeit, my examples do not show lines on reverse.

OK, let's say, your stamp is either...
1. Unwatermarked
2. Unwatermarked (a stamp position that lays outside the margins of the dandy roll)
(I am not privy to that info.)

Then, your stamp can only be
Stanley Gibbons SG# 1,3,8,9, or 10.

8,9, and 10 are the low value examples (22 shillings 1993)
wmk small star (sideways)

Best I can do, as a novice.

Looks again like a stamp printed on the sheet margin.

Rod

I have one without lines but the lines from the front are clearly visible on the reverse.





The vertical lines of the stamp of the OP don't look like any watermark I've seen before.

Thanks GO,
Suggestion: maybe differing paper.
Lovely stamps,are they not?
Yours will be crown over CA ?
The engine turning is exquisite.

Tip: look out for Postmark "A12" on these, =St. Christopher.

Further reading on SCF
https://goscf.com/t/28084

Rod

Thanks for the link and the tip. They are beautiful stamps. Don't find them often enough to complete a collection.

Thank you all for your help!
Cheers!
Mick