Both notebooks have largely the same text (they are different versions of code I'm developing). Both have only "math" cells (no text, title, etc). If I "Show ruler" on the two, they both display a ruler with 1" on the left of the window and 8.5" on the right. Yet one, when opened, fills my display (1280 x 1024), while the other takes about half the screen. [Of course, the first shows letters twice the size as the second, as it is two times bigger]. As far as I can tell, the only difference between the two files is the size of the screen appearance.
Where (and how) is this set, specified, or changed?
Aha, I figured it out! However, I'll still post this, including "how I did it", as it may help others delving into Mathematica arcana.To see where the "significant" differences lay between my two notebooks, I used a "programming text editor" to compare the .nb files, looking for differences that "made sense". There are a group of cells at the "End of Notebook Content" that include WindowSize (factor-of-two different between the notebooks), and the "big" notebook had a "Magnification" entry that the other did not. Using Help, I found that Magnification can be viewed (and set) with the Option Inspector. Sure enough, using the Option Inspector on the "big" notebook showed Magnification (under Notebook Options, Display Options) was 2, and changing it to 1 made the notebook appearance consistent with the second notebook.
