CL,
The scales 'transition' in size and shape on a typical skin.
The source of crocodile skin is important for acceptance of importation. For example porosus crocodile leather is acceptable from sustainable sources like Australia but not Indonesia.
The scale sizes transition from large to small across the animal. There are sections of scale irregularity if required.
The fashion for watch straps has swung between small and big scales to-and-fro over the years.
Originally because it was difficult to fake small or big scales. However, today's technology is so good that fakes of any size are possible.
You just have to use reputable suppliers.
Watch straps tend to have smaller scales because the biggest scales are more suited to jackets or handbags.
In the pictures below, you can see how the desired sections can be cut from the whole skin.
Regards,
MTF

Raw hide

Bleaching and QC 
Leather works

Crocodile and Alligator leather

Crocodile and Alligator leather

Crocodile and Alligator leather