Caldercraft Model Boat Fittings 8103SW 3mm Single block. Walnut.
Sold In packs of 10, these single blocks measure ((h) x (w) x (d)) 3.6mm x 1.9mm x 2.4mm and are available in walnut.
Equivalent manufacturers part number cross references:
Artesania AL8516
Caldercraft 8103SW
Disar Models DM11001
Mantua 37000