Urgent- Is a rocker arm a rocker arm?

[Peter Jackson]

I am installing my S3s and was replacing some semi scored OE rocker
arms. using 13257-53J03  Car is apart.

I noticed that there is a number stamped on the back of the arms.
They do not match the numbers on the rocker arms coming off.
Is this a grade measurement or just a manufacture code.

Big Question--
Is a rocker arm a rocker arm or do they come in different grades like
bearings?

I'm on Digest so please respond directly.

Peter J
96 SE-R