It's just contract optical work. I don't know if B&J had their own optical shop or designers, or contracted some or all of that out; the answers might be in old posts; but many sellers did something like that. (For example, many of the lenses branded "Calumet" made by Ilex, Schneider, or Rodenstock have excellent reputations.) The exception may be that there are some lenses marked Dagor that B&J assembled from old stock that have a mediocre reputation, but I've never actually seen one of those.
You can count reflections of a flashlight in the lens elements, with the shutter closed so you count the front cell and rear cell separately. By moving the light source back and forth and watching which way the reflections move, you can often figure out whether they are coming off convex or concave surfaces.
Looking through the clipped corners of a ground glass to see whether you can see the lens helps measure the circle of illumination, but the circle of good definition can be smaller. For example, many lenses of Tessar design (very common) will illuminate a large radius but the definition becomes very poor in the outer parts. (IIRC, Richard Knoppow said the design had a radius beyond which it became very astigmatic; this is often called "swirly bokeh" because images become tangentially elongated.)
Anyway, there isn't a great substitute for testing the lens as you might intend to use it. For 8x10, paper negatives would probably be fine - maybe try focusing the camera on some scene with a lot of detail, adding an inch or two of front rise, taking the picture, and examining the bottom corners of the negative (top of the scene). Obviously, you have to have detail in the scene - if it's blank sky then there won't be any information. On the other hand, if you typically have blank sky in the top corners, then maybe you can get away with pushing the image circle anyway.
You can count reflections of a flashlight in the lens elements, with the shutter closed so you count the front cell and rear cell separately. By moving the light source back and forth and watching which way the reflections move, you can often figure out whether they are coming off convex or concave surfaces.
Looking through the clipped corners of a ground glass to see whether you can see the lens helps measure the circle of illumination, but the circle of good definition can be smaller. For example, many lenses of Tessar design (very common) will illuminate a large radius but the definition becomes very poor in the outer parts. (IIRC, Richard Knoppow said the design had a radius beyond which it became very astigmatic; this is often called "swirly bokeh" because images become tangentially elongated.)
Anyway, there isn't a great substitute for testing the lens as you might intend to use it. For 8x10, paper negatives would probably be fine - maybe try focusing the camera on some scene with a lot of detail, adding an inch or two of front rise, taking the picture, and examining the bottom corners of the negative (top of the scene). Obviously, you have to have detail in the scene - if it's blank sky then there won't be any information. On the other hand, if you typically have blank sky in the top corners, then maybe you can get away with pushing the image circle anyway.
