Similar to the model no. 630, which is a modification of the standard model no. 620, there was also a version of the model no. 623 with asymmetrical aluminum or steel scales, in this case the model no. 633.
This model was available in aluminum and in guilloched steel scales, either with or without a key ring. These pocket knives with the special scales are rare. From the mid-1970s at the latest, production was completely discontinued.
The special scale shape of these pocket knives, called "dogbone", was only available in 58 mm. This scale shape allows the tools to be opened without having to use a nail hammer. The tools, which are easy to grasp when closed, can be opened by pressing your thumb and forefinger together and moving them sideways.
The disadvantage of this scale shape is that the tools are still clearly visible when closed and are therefore poorly protected from dirt or lateral abrasion.