K31 No Serial on bolt?

Picked up my new K31 this weekend. It is a fine one. All the serials match including the wood.
It had the slip of paper under the butt plate with the owners name, birth date, address, and unit (Howitzers) However there is no serial number on the bolt. Is this normal?
It cocks and locks up fine, but I had read and watched videos that said watch for the serial mumber to be on top when the bolt was locked in???

The part of the bolt where the serial number is placed is the bolt locking sleeve. If it has been replaced due to wear or defect the new sleeve will not have the serial number on it. some are force matched with an electro pencil but are often poorly done. Personally i prefer to leave it plain. congrats on the new rifle