All of the Hornbeam family have characteristics that make them very good for bonsai.
Happy living in pots and a response to pruning that results nicely ramifying branching. Leaf size is generally quite small and reduces further with time under a bonsai regime. A number of the Oriental species are pretty much classic subjects in the bonsai world but the native European species are certainly being seen more often as well developed bonsai now.
This little bonsai is full of interest. It is likely to have been an import from Korea some years ago. At 23cm. high, by height it can be in the shohin class although to me it feels more like Kifu or even chuhin with a branch spread of 28cm. It is grown over a rock and above the rock the trunk measures 3cm. in diam. At soil level root and rock are 12cm. across. There is great character in that little trunk though with twists and hollows. The pot is a nice Chinese unglazed ceramic rectangle 21x15x6 cm. A bit more branching and ramification requires as a next step which is basically grow and prune.