Alan, those pattern welded swords which can be attributed to roughly 200AD (the latest coin found there is from 187 AD, one can only speculate, that the swords were not necessarily new when their offering took place) are absolutely certainly Roman and absolutely certainly not Danish. Swords with no pattern welding could be of different origin.
To reach such a level in pattern welding seen in those swords - there should have been a way longer then a generation or two from simple piling of rods to pattern welding displayed here. These are patterns, of which a Merovingian, 2 centuries later, didn't even dream of, not denying the mastery working with twisted rods from 5th cent. onwards.
The people who till now are of oppinion complex pattern welding started in 5th cent. are repeating information, which is more then 80 years old and certainly outdated. According to Arbesman...
The drawings I posted can be found in this fantastic publication, which should be in the library of every person with deeper interest in the history of pattern welding:
https://www.abebooks.de/978878841538...qfFM7ZJ-_9rwqw
Vol.11 - text, vol. 12 - drawings and photographs.