I’m sorry to come in with a negative comment.
The OP’s item would be known as a crystal ball. Omega definitely made the crystal ball (at least from 1894) with both the 30’’’ and then the 27’’’ 8-day movements.
According to Omega’s AJTT (for the OP, ‘A Journey Through Time’, Marco Richon, 2007), the crystal ball had movements 30/40’’’ and later the 27/40’’’ … BUT … “smaller pieces, equipped with the 19’’’ calibre and often found in antique markets, are not original”.
The movement in this watch is definitely NOT a 27’’’ 8-day nor a 30’’’. It looks as though it could be an ‘original’ 19’’’ (from the mid-1920s). However, according to AJTT the whole item (thus the crystal ball watch) is not original.
The OP quotes the ‘Omega Store in Austria’. I’m sorry but the Omega Store would not be able to confirm original numbers. It is quite possible that the movement (with the number that we see) is original – but to confirm originality there would have to be a case number (which I think is very unlikely) and that could only be confirmed by Omega Heritage in Biel/Bienne (the ‘Omega Store in Austria’ would not have those records).
As Jim says, “99.9% of the smaller ones seen on eBay etc are fakes” – and as WatchTimes says, most of the fakes come out of China (invariably with a sweep second hand!). This is not the typical Chinese fake – but it is also not an original Omega 30’’’ or 27’’’ 8-day crystal ball.
My guess is that it was a ‘project’ made by somebody who used an original Omega movement (probably 19’’’). If the OP wishes to confirm it further, he would need to provide the case number (even if he asks the ‘Omega Store in Austria’ to do that for him) – without that, there can be no question of it being original.
As for value, in my opinion not very much.
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