Hallo, I think by comparison with other stamps (https://goscf.com/t/44950) this is Special Printing by Continental hard, bright-white wove paper. I have not a declaration, the paper is very different.
If you really think it is a Special printing, then you must submit it for an expert opinion. Deciding whether it is worth submitting is up to you, but this list will not be able to offer much help, except for general comments. One must have the stamp in hand and the experience to know the differences. Few here have ever even seen one, and could hardly advise.
However fewer than 10 examples of #181 have ever been certified, and none of these is used. Think about it.
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