Caldercraft Model Boat Fittings 8105DW 5mm Double block. Walnut.
Sold In packs of 10, these double blocks measure ((h) x (w) x (d)) 5.1mm x 2.7mm x 3.5mm and are available in walnut.
Equivalent manufacturers part number cross references:
Artesania AL8526
Caldercraft 8105DW
Mantua 37060