They seem welded, the base is flat clean, no joints. Must be a first but I wouldn't be surprise to see an explanation from more experienced folks here. Unique find and congrats!
That is the COOLEST coin jewelry (?) alteration I have seen in a long time. I see there is only one hole, and it may be tapped for a screw? I wonder if it is utilitarian and not an adornment. Part of a home-made tool or utensil maybe? Congrats! Sub