Undiluted, he is quite sharp with the 51.1%.
In the nose I find distinct sherry notes with a blend of raisins, oranges, cloves and dusty wood. Already delicious, but now nothing special (does not have to).
The palate is initially round and strong, but undiluted always resonates with the unpleasant alcohol.
The quite delicious aromas of the nose unfold unfortunately on the palate not quite as transparent.
Instead, dry espresso notes, dark chocolate, wood, pepper and a subtle smoky note are reported (especially in the finish).
The finish is unfortunately rather short and dry.
Conclusion: That's okay, but I think he is too vague (also has "flavor holes") and too much of the alcohol coined (the sharpness). With addition of water, it does not get better or decomposes the aroma game eventually complete. The age of 23 years I would blindly probably not nearly touch.