I too admire the workmanship of these rifles. The edges on my Marlins, old and newer, are sharp and clean; everything fits well and tightly.
Keep in mind that Marlins have always been made for working class hunters who needed a functional, effective and CHEAP rifle. Those tool marks are found inside expensive firearms as well. Look inside Winchesters of the same vintage. Those tooling marks usually don't interfere with action and too much stoning/smoothing may make the actions overly sloppy.
Cleaning the crevices and wood in an old well used Marlin is only necessary every hundred years or so.
Here is a great reference for fixing the Marlin jam. I keep several spare carriers in my tool box for this problem. JB Weld can be used in some cases.