A further optical criterion is the handle.
Is the handle firm or wobbly?
Has it been wedged properly?
Are there any tears or insertions visible?
Is the handle made out of qualified wood?
Permitted is wood which is according to the Technical Delivery Terms and Conditions DIN 68340, and qualified are ash, hickory and acacia. The wood should be long fibred to avoid breaks in case of an off target blow. The fitting of the handle must be checked carefully especially with steel, plastic or glass fibre handles. Fitted handles must be bonded very firmly.