Any reason for notches on fish knives and fish forks? (and more)

[perfection]

It does arouse my curiosity to ask what practical purpose the notch on a fish knife serves?

What about the pair of notches on a fish fork?

Since i have never seen an original fish fork except the modern ones 'used in catering colleges, may i ask whether it it is true that the left time is thicker an larger than the other 3?

Why do i see so much similarity between the notched style (master) butter knife and a classic fish knife? Are they different in height or blade width?

Are the more modern "stepped" butter knives with just two similar blunt edges 'stepped" for any particular reason?

Thanks for any contributory answers with regards the above