US Scott # 489 Perf 11 Questions

Hello, I have what appears to be a 1917 US Scott # 489 Washington 3c violet coil stamp with a horizontal perforation. These are cataloged as having a horizontal perf 10. However, my stamp is perf 11. I tried doing some research but was unable to find this anything like it so here are my questions?
1. Is this a Scott # 489 stamp and were there any made with a horizontal perf 11
2. Or, do I have another issue? and is it a different Scott #.
Thanks.
-Tom

As requested, I uploaded the image with the perf gage overlay.

Really need to see a pic.

OK, I think I know what is going on. The right side perforation is cut and so it looks like a horiz perf coil stamp but it is not. Looking carefully at the right side your will see perforations. I believe this stamp is a 1918 issue Scott # 529

It is not a coil stamp. It came from a pane, not a coil strip. Note the small amount of perforation still remaining on the trimmed right side.

Thanks to all who helped me with this. I just wasn't looking closely enough. Regards.

Much easier to see when the image, as posted here, is many times the size of the actual stamp. We all had an advantage thanks to you.

It looks like Scott 501, the regular issue p.11.

You can learn more here https://stampsmarter.org/1847usa/wa...d33perf.html
and here
https://stampsmarter.org/1847usa/WFFakes.html
Don