Timelines Original Selling Artefacts From Pre-War Polish Museum?

VO 012037 Rare Viking 'Iron' Snaffle Bit
Iron, 115 grams; 276.66 mm. Circa 9th-10th century AD. A rare and very well preserved iron snaffle bit; two large rings that would receive the reign (sic!) guides and cheek pieces are connected by three bars, two looped ended bars connected to the rings with a central S shaped bar between. A very plain and common type during this period but rarely found in this state as the iron does not survive. Ref: Similar to Luistari-A History of Weapons and Ornaments; G 825/7, plate 34. Very fine condition. Ex the family of an old man who was a keeper of a small town museum in Poland before WWII.

Before the War, as after the War, since the antiquities preservation law of 1928 all archaeological finds in Poland belong to the state. Under what circumstances have the sellers ascertained it left the country of origin? If this object was taken from that (we note unnamed) "small museum" and has no other paperwork, then it is most probably stolen. If so, why is it being sold openly in Upminster? How many more Polish artefacts are Timelines selling? I thought they belonged to a group of dealers with a strong Code of Ethics, so what is going on?