Just like the title states. What are the numbers that are handwritten inside both the right and left insides of the grips/stocks?

I recently bought a set of Goncalo Alves, smooth Target stocks for my 640-2, which give the gun a musch better feel, and they are factory made. Just curious as to the numbers written inside.
I have seen many sets of S&W stock sets wit hthese markings, but never asked why?

Can anyone shed a little light?

on older guns the grips were numbered in pencil on the inside of the grips to match the ser. number of the gun. if your grips are newer ones i would think it would just be a stock number.

Sometimes just a number to keep the matching halves together.