Possibly Hanami Nashiki. Leaf shape and coloring fit. Leaf size of Hanami Nishiki are one of the smallest found on Japanese Maples.
Thanks. It's definitely not 'Sharps Pygmy' then? I want to be sure because I already have 'Sharps Pygmy'.
How big/small are those leaves? There is nothing in the pix to give a sense of scale (like your hand, a ruler, etc.). I have an Hiname Nishiki as well. Size is a big factor. Leaves on Hiname Nishiki. loosely speaking, are 'thumbnail size'.