Murano made many paperweights with 'commemorative' dates within them. I don't think they were trying to deceive anyone. At one point on this forum (or another - I don't recall which) we tried to see how many examples of different dates we could find - I don't recall the final total, but it was at least 6. 1852, 1856 and 1885 were quite common, and there are some from the 1950s which were issued at the time.
The Arculus / Walsh Walsh '1848' date - which led to the incorrect 'antique Whitefriars' attribution in the USA - was put in the paperweights in response to requests from wholesale customers - the factory did not sell direct to the public. I have just been corresponding with a man in his late 80s (whose mother was an Arculus family member) who used to make the set-ups with fake dates when he was a young boy.