On those Feather Professional 60's is there a slider on top? (looks like there is not).
Is that a small hole in the face of the razor? Possibly where the spring is mounted? Do you understand why it is there? Looks like a way for water and soap to enter. Thanks for posting the pictures, your razors look nice.
Yes the hole for for the mounting of the spring.
I believe it shave the same as the modern Artist Club DX as the geometry is almost the same.
Most probably, I will not going to use it as I still got many other Artist Clubs.