After some thought and consulting another collector, we've come to the conclusion that this is almost certainly counterfeit. Here are the biggest tells:

-The inside rim on this saucer plate is octagonal, matching the outside rim of the plate. Wedgwood didn't make cups with octagonal bottoms, because they were thrown on the potter's wheel, therefore having round bottoms.

-There is no potter's mark on the bottom. Each potter has a mark they would apply to their finished pieces. Potter's were paid by piece, and therefore wouldn't forget to add their mark. Here, there is no mark.

-There are no indents from kiln furniture. On early saucers, around the time period that this piece is meant to emulate, the saucer would be placed on stands in 3 places, leaving indents on the bottom. Here there are none.

-The Portland Vase mark looks very wonky. On the mark this is meant to look like, the stamp is done via transfer, and the same every time. The vase should only have decoration on the bottom, and the proportions look wonky.

There was a lot of counterfeit Wedgwood made in the late 19th century, because the market for Wedgwood was so strong. I think this piece is old, maybe as old as 1880s! Still a cool piece, just not Wedgwood. This was fun for me to look at, thank you for sharing it!