N266 == 1974~1977
The rear sight may be from a different N-frame revolver.
There may be a good reason why the target grips don't fit seamlessly.

If you post your Model 28-2 in the forum in its own thread, you may get more specific answers.
N-frame Tyler adapters can be hard to find, N-frame Magnas are easier.

In any case, the condition of the gun seems to be very good, which is what matters. Enjoy!