Raleigh Sports Serial Number

[King Raleigh]

Hi. New member here. I have a 1976 Ladies Raleigh Sports and I don't know how to read to the serial number. This Raleigh has the serial stamp under the bottom bracket instead of on the seat tube, and seems to be coded differently; while the regular serial codes for Raleigh Sports had 2 letters and then about 7 numbers, this Sports has simply four numbers, and they don't even look like they were stamped well. No letters.

I've heard of Raleighs with 531 seat tubes being stamped differently. Does anybody know if this is a 531 seat tube AND how to read this serial code?

Thanks in advance,
-King Raleigh