1951
The Singer 401A was manufactured in 1957 at Anderson, South Carolina.
That singer model was manufactured in 1955 according to the Singer model number guide.
2915
In 1951, a "Limited Edition" of only 10,000 "Singer 301" sewing machines was released to commemorate Singer's 100th year Anniversary, 1851-1951. They were manufactured at Anderson, South Carolina and are the only Singer 301 sewing machines manufactured and sold in 1951. The Singer Model 301 were manufactured in 1952 at Anderson, South Carolina, except for the "Limited Edition Singer 301". The Singer Model 301A were manufactured from 1953-1957 at Anderson, South Carolina.
Your Singer Model 301A sewing machine was manufactured in 1953 at Anderson, South Carolina.
The two letters (NA) at the beginning indicate 1951according to Singer's site in the related link.
Singer 401A was manufactured in 1957 at Anderson, South Carolina.
2345
Machines with serial numbers beginning with NA were manufactured in 1951.
It was manufactured in 1957 in Great Britain.
To check for divisibility by three:Add together the digits in the number. If the total is a multiple of 3 then the number is divisible by three.E.g. 5830. 5 + 8 + 3 + 0 = 16. Since 16 is not a multiple of three then 5830 is not divisible by three.