I, too, found the (cheeks in my case) inside of the infill plane making final adjustments to the bed and sole plate. On both of my first two planes. I didn't pay attention on the first because I figured neatness didn't matter- i wanted to see if building the second one was worth chasing after.

Since then, I've tried to do everything well on the first of anything even though the first of anything new is always filled with errors. if five errors are made, it's nice if they're in the first one.

I'm sure you're more creative, as I am, in modifying tools that would make those marks in the first place so that it's not possible for them to be made easily...at least where practical.

re: the beech in norris planes - I had three with beech. All three had significant shrinkage over time - no matter how well seasoned beech is, several decades of seasonal minor shrinking and a less than 1 springback factor will leave things undersized. I'm thinking that's a good bit of the reason that a lot of the planes made by patternmaker's and craftsmen to avoid buying a full priced plane - early on (before beech norris planes) were mahogany. I wouldn't be surprised if the beech in your norris just shrunk in length. I no longer have any of the three (two A5s and a long try plane that I can't remember - same style with the adjuster, though, just a U channel sole try plane - also A5?), so I can't look at them.

The try plane worked surprisingly well. The two A5s had moved a lot and more than just shrinkage and I was happy to see them go. Probably just bad luck. The try plane with the U channel had big visible gaps between the wood and metal, but if a plane works well, it works well.