Thor, and Pete, * Edited for clarity*
The Circular Markings are the typical marks left by a dull End Mill with Corner Radius.
The Longer Straight Marks appear to be the result of hurriedly removing,(with a hand scraper),the heavier rough circular marks, produced by more rapid feeding of the tool due to stepped up production practices.
Until late in WW-2, the standards of finish was a matter of judgement of the inspectors visual inspection
In my opinion both of these finishes would have met the same standard of finish though widely differing in appearance.
The standards were specified in the USA by a letter or number within check mark touching the surface. such as P = Polished, G = Finish Grind
1 = Fine machine finish,
2 = medium machine finish,
3 = Rough machine finish,
4 = rough hand grind,
5 = Burned surface or rough scale surface.
I feel that the finish that we are seeing would meet the V2 finish standard. Which was the usual finish for non critical surfaces, called good machining practice
Today the standards are specified as V1, to V500
Where the digits are measured in micro inches.
As Best I remember,
ViggoG
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