Savage 99 serial numbers

[Big block]

Hi all ,
Recently acquired a 1941 Savage 99 in 300 Savage.
My question relates to serial numbers.
The fore stock serial number matches the receiver serial number.
The butt stock and butt plate numbers also match however there is a second serial number stamped in both of these.
The matching number is 407xxx and the additional number is 406xxx.
It is the same additional number on both these pieces.
Did Savage ever repurpose parts from stock?
If the stock was replaced by a previous owner why would one stamp the matching serial number on these parts as the other number is still present?
Note: the font is the same.
I don't know that these parts were switched out or when but what are the chances of finding parts for a gun that old with the serial numbers only about 1000 units apart?
Thanks in advance

[snoeproe]

I also have a 1941 man 99 in 300 sav. It’s an EG with serial 409xxx
It’s hands down my favourite hunting rifle.