He was a physicist and author with an interest in old technologies. I believe that most of van Leeuwenhoek's microscopes are replicas, but their basic form is well documented. As I recall, the most difficult thing to replicate was the lens, which he made using the same method van Leeuwenhoek's used: dropping molten glass through air.

The telescope was relatively easy in comparison. He used two lens from his stock of lenses and simply mounted them in a tube. I recall him having fun with the decorations, which are quite detailed.

He was so good at making/repairing ancient technology that the Science museum trusted him to repair some of their most precious items from their old wireless collection. He used vintage brass (modern brass looks wrong), vintage ebonite and authenticity old mahogany. Wish I could remember more. I have a few more of his things: a set of Napier's Bones (an old calculation device) made from chop sticks, an reproduction crystal set, a number of orreries.