Please add 1931 The Netherlands 2.5 Gulden, PROOF type

There was a Heritage auction recently when a PCGS PR61 1931 2.5G Wilhelmina was auctioned:

https://coins.ha.com/itm/netherlands/world-coins/netherlands-wilhemina-i-proof-2-1-2-gulden-1937-pr61-pcgs-/a/3053-37819.s?ic4=OtherResults-SampleItem-071515

According to the listing this is the second known

Is there any reason, apart from the slab text, to assume that the auctioned coin is a proof? Lying slabs are not as uncommon as we all would like to be. Personally, I don't think it looks anywhere like a proof.