This is the ZIG Art and Graphic Twin marketed by Kuratake.co.uk. Their full range can be found on their website. I've been trying one out on a sheet of A3 Canson.
The drawing shows a sketch of a jackdaw but the brush drawings were made with the brush end of the A&G Twin washed over with a colour brush loaded with plain water. I've doodled with the rubber marker tip which gives a fine even line. These can also be softened and washed over to good effect.