Hey Brian. There are a number of different extrusions that will occur before it become a fully modeled, 3D piece. That might account for the inaccuracies you mention.

Yes, there are tiny differences to be found in old blueprints. After all, they were done by hand! We take for granted .000001" accuracy, and use it even when it isn't really needed.

One thing I have learned working with these old documents, "back in the day", they were a lot less about aerospace tolerances and more about proper function and longevity. Most times a 1/32" was "good enough".

Chris