Help with this well-crafted credenza/sideboard  

Judging by the handles, try Clausen & Son.

Dovetailed corners in m

Thanks for the input. I've owned a few Clausen & Son credenzas and none have had this quality of construction and materials. This is just over an inch wider than the typical Clausen and also never seen a 4 door Clausen.

@leif Anyone else you know who's used this technique?

Unfortunately the observation about the bottom of the piece is unlikely to help identify it much. Nobody photographs there.

I would take more photos of the hardware, door slides, back, handles, etc etc and start looking for similarities. Those are all thinks you have a hope of finding in a photograph.