The teeth on a scutch comb should have a defined square edge.
You should not be able to bend the teeth with a hammer (they should break off before bending).
Check the thickness of the scutch comb/drove, as the thicker the cutting edges, the longer they will last. The average thickness of a scutch comb/drove is 3mm.
Check to see if the scutching tool has any dirt or damage to the steel as this can increase the rate of the product’s deterioration.
If you are buying from the internet, try to purchase your tools from a reputable manufacturer.
A responsible manufacturer will offer relevant product knowledge and in some cases guarantees which can prove their trust in the product’s quality.