I used the method described by Professor Keeling at the University of British Columbia to measure the magnification of a couple of the Bancks lenses and one of the glass bead lenses that I made. Dr. Kelling's method is very well described and written, it can be found at this link: http://www3.botany.ubc.ca/keeling/resources.html
I was a little surprised by the results, but this is what I came up with:
For the #3 Lens from the Bancks 1825 microscope, 10.9x. I was a little concerned because I felt like I had a lot of diffraction or something that caused the image to look blurry, so I am not sure if I was getting an accurate measurment on the size of the grid hole.
For the #2 Lens from the Bancks 1825 microscope I had a much sharper image and came out with a magnification of 51.5x.
I also measured the magnification of one of the glass bead lenses that I made using the method described by Keeling and I came up with 139.8x, not too bad.
I was surprised by the results for the Bancks lenses because I felt that I was able to see some remarkable detail with these two lenses so I was expecting the magnification to be a bit higher. It is quite impresive what you can see with 10 and 50x!
When I get to making my own lenses I will keep this in mind and see if I can achieve some similar results.