the bottom may have trimmed perforations; the bottom edge looks very suspicious to me.
Don't overthink Washington/Franklin stamp ID. Once the type established, and it was as a type II, the stamp cannot be a flat plate sheet stamp.
The key attributes of the stamp, including color, printing quality, design size, margin size, die type, paper, perforation alignment and general appearance point to Scott 454 with a vertical watermark.
I went back and looked at the original image from the OP. Type II characteristics are visible, despite the small size of the images. The watermark on the lower left corner of the back image is readily apparent. Scott 491 examples are found on a coarse, less bright paper of variable thickness, as are some Scott 454 examples.
Direct examination by an expert and VSC-6000 or equivalent is needed to confirm that no watermark exists. While faint partial "S" shadows exist on some unwatermarked paper, an expert should be able to tell the difference.
There is no need to speculate, invent varieties that cannot exist or misread the Scott catalog. I doubt if any expertizing committee would accept the stamp as a Scott 491.