Trouble Identifying 3 Cent Washington

Hi Folks,
I am having trouble identifying this 3 cent Washington below. It appears to me to be a Scott #535 Type IV. I am thinking it must have started life as Scott#535 but received Shermack perforation. I am working from a 2018 Scott's Pocket catalog so I might be missing the Shermack annotation in the catalog. My 1937 Scott Catalog makes no mention of the Shermack perforation either that I can find.
Am I thinking correctly?
Thanks,

Chris

Some links which might help
http://stampsmarter.com/1847usa/was...pesMain.html
http://stampsmarter.com/1847usa/was..._02main.html
http://stampsmarter.com/1847usa/PrivatePerfs.html
http://www.stampsmarter.com/1847usa...ntifier.html

Don

Thanks for the link, Don. I knew the information had to be on the site somewhere. I searched for Shermack and could not find it. I guess it would have helped if I spelled it correctly!
So, it appears that Scott did not assign identification numbers to the stamps that were privately perforated - like the Schermack. They only assigned ID numbers to the stamps perforated by the BEP and to imperfs. Am I thinking correctly?

Thank you,
Chris

Yes, you are on-track that this started as a 535 with the Schermack Type III perfs added. The Scott U.S. Specialized catalog has a Back-of-the-Book section for these vending and affixing machine perforations. It would be good to upgrade to the larger catalog.

Thanks. I am looking for some used ones. Is the specialized Catalog where I will also find the watermark types? I have a lot of worldwide stamps, too.

Chris