Amal Concentric Carb Drain Plugs
691-622155 & 691-622155/B
Two options available from British Cycle Supply.
691-622155 Drain Plug for Amal Concentric Carbs, Knurled Brass, uses washer 691-622151, sold each
691-622155/B Drain Plug for Amal Concentric Carbs, Hexagonal Head, Brass, with washer, sold each
691-622155/B pictured