I have Janome machines and if you inspect the bobbins that come with a new machine, or are sold under the Janome brand, they have a letter 'J' impressed on the centre of the bobbin. It can be difficult to see but it's there
Yes, get a magnifying glass and a good light ... a teeny clear impressed mark on a small clear thing aint that easy to see ...
I wish they did that with other Big name machines, it would take some of the guess work out of things ... like Brother embroidery bobbins.
Anyway pretty soon will have two specific to Elvistoo bobbin cases to keep things separate.