Now we're getting somewhere. Mr. Henry Stolow was an infamous stamp dealer with a history of fakes, forgeries and made up stamps. An examination of the back reveals the extensive thinning. But we can also see the J&H Stolow brand at the bottom right:
If this is in fact a real Stolow piece of fakery, the stamp would be an interesting curiosity to have in an 1898 revenues collection. Just don't put it into an album spot marked R190a! Also, don't pay $299.99 for it. Maybe $5.00?
Thanks to David Thompson for calling my attention to this item.