It certainly has pins in the normal places. They must have been ground down after they were installed, making them extremely difficult to see.

If it was mine, I would grab each side of a link with a pair of pliers, and alternate between gently squeezing the sides together, and pulling them apart, with a very slight twisting action. I'm not trying to take it apart yet, just get enough movement in the pins to be able to identify them. Once found, remove like normal.

They may be extremely difficult to reinstall...

You could try some of the tricks used to expose the layers in Damascus steel: etching with various acids. The differing steels of the pins and the links may etch differently, revealing the pins.

Edit: at the time of this edit, not one other comment has even attempted to address OP's question. The only other suggestions have been to move the pin in the clasp (which is so bleedingly obvious that I can't believe that OP could have missed it; OP needs adjustment beyond the limits of the clasp) or to just buy a new band. (Again, bleedingly obvious).

What I described is certainly feasible for a patient and moderately skilled craftsman, and does not preclude the "advice" presented in other comments.

OP, consider hitting the pliers with an engraver while gently pulling. The vibrations may be enough to move it. If you're familiar with how metal reacts to a torch and can avoid overheating, a butane torch might help the pins begin to move.

Remember: you're only trying to find the pins. You'll need to punch them out.