Not exactly sure but on a B (it should be the same) it is on the right side of the left-hand seat mount.
You should be able to get ahold of Farmall and they should have records. Although I am not for sure.
A Farmall A with a serial between 281569 and 300125 was made in 1950. Source: http://www.geocities.com/mck357/serialnumbers.html
Farmall serial number 126516 corresponds to a Farmall H tractor, which was produced by International Harvester. The Farmall H was part of the Farmall line and was manufactured primarily between 1939 and 1953. This model is known for its versatility and was widely used on farms for various tasks.
The Farmall M with serial number 123030 was manufactured in 1952. The Farmall M series was produced from 1939 to 1954, and the specific serial number indicates its production year within that range.
fbk-94458
You can check at TractorData.com or link below
On the metal tag on the side of the bell housing.
Check at TractorData.com or link below
You have to compare the serial number to a chart that shows what year it was made.
what is the serial number ????
Proofhouse.com has Winchester serial numbers.
you will find it on the barrel or action of the firearm