Collapsible Summicron 50mm f2. This example is the so-called radioactive Summicron, made with thorium glass. The radiation level has been confirmed with a basic radiation meter. Serial number in the 1,040,000 range, manufactured in 1952. Distance scale in feet. Leitz product code: SOOIC.

As is typical of thorium Summicrons, the glass has developed a distinct yellow tint. This example has a particularly deep yellow coloration, comparable even to the early under-one-million examples.

The radiation reading was also quite high compared with the many thorium Summicrons we have handled over the years.

Due to the yellowing, it may produce slightly higher contrast when shooting black-and-white film. Comparing it with later Summicrons made with standard optical glass should also make for an interesting photographic experiment.

This is a well-preserved example for a thorium Summicron, showing relatively little use. The collapsible barrel also has only minor wear.

A full overhaul, including focus adjustment, was completed in September 2026. The aperture ring and helicoid operate smoothly with a nicely damped feel. Rangefinder coupling is also accurate.

There are minor cleaning marks on the front elements and some coating deterioration on the rear element, but no haze is present. Many thorium Summicrons suffer from considerable deterioration of the glass, but this example remains in very good optical condition. A scarce example.

An original Leica front cap is included.