The photo of the ring holding the cord in post #1 looks similar to mine.
They could be the same rings.
I suppose one could carefully drill out the cord and leave as is, or insert the new type cord.
I have not attached the cord to mine.
The Docter 10x25 has a cord attached. I never even bothered to see if it comes off.
The image with my 10x25 Trinovid is considerably brighter than the old Docter 10x25. The edge performance is sharper in the Trinovid. But the Trinovid has a bit more edge CA.
However, I use the Docter 10x25 as it is so fast to use. The Trinovid is fiddly, more jewel like. Small focus wheel, and more difficult to get the right IPD.
So for me image brightness is not the major factor.