There are two types of scutch comb: those designed to cut marble and those for use on stone.
The difference is in the number of teeth, as more teeth are needed to cut through marble.
Marble scutch combs
A marble scutch comb has 7 teeth per inch. The more teeth per inch, the sharper and finer those teeth tend to be. This helps when it comes to cutting marble, which is a fine grain stone that needs fine teeth to cut it.
Stone scutch combs
A stone scutch comb has 5 teeth per inch.
The best scutch combs to purchase are those created for hard bricks/stone (the marble scutch comb) as they are universal in cutting both hard and soft bricks/stone.