21 Stud block question

[russcc]

I have what appears to be a bare 21 stud NORS service block. Are there any identifying numbers in the casting. There is large 38 cast into an area inside the block. See photo.
I have never seen a block where the interior water passages looked new like these. Is there a process to clean them to the point they look new with no rust damage. Even the thin casting flash in the water passages looks brand new.
Also, do all 21 stud blocks have core or freeze plugs in the pans rails. See photo.
Those plugs might have saved all the 24 studs blocks I have seen with cracked pan rails from freezing.