If this gun was a "best" gun, then why isn't the lump that can be seen on the underside of the action fully engraved ?

I think the lump shows the style of the gun when it was made.

I have quite a few of them and my Rigby lump is engraved
similar to the rest of the gun but the others doon't all have
engraving as the action doesn't.

Anyone like to comment ?