Very interesting - is this lens a simple crown element or is it an achromatic lens? If it's a simple crown element, it would be interesting to try it with a strong filter to reduce chromatic aberration.
Used uncoated plano-convex lens, 40mm diameter with 400mm FL. Least expensive one from Edmund Optics that I thought would do the job (just in case I screwed it up).
I still need to make stops for it, and I have a plan that involves adhesive backed magnets and tin!