stole this picture off someone but i can't be bothered uploading one of my own.

i have these numbers on my 11 stud head with large valves.
i know that it was also fitted to the 1300's and mk3 cooper s but i have seen other people have the same 12g1805 number but with a "k" or an "a" stamped there instead of the "s" that i have? any info would be great!!!
bear.











