23a Pulley with boss ½; 12.5mm. First.pair Meccano England, brass paint on brass associated with early to mid 50s set 3. Next, in plain brass with domed blackened grub screw, belongs to a mid 60s Magic Motor in red & yellow flap end box, and finally, in a redder brass, from a 1974 4X with Triang manual and note about Hex nuts. OPM mentions that later smaller parts were not stamped, but there's also a chronological clue as to when they stopped putting a brass colour coating on parts that were brass anyway...