An early collapsible Summicron 50mm f2. This example is the so-called radioactive Summicron, fitted with thorium glass elements. Confirmed with a Geiger counter, and it produces a fairly strong reading. Serial number in the 920,000 range, manufactured in 1952. Meter scale. Leitz product code SOOIC.
This lens appears to use two thorium glass elements. As expected, the optics show noticeable yellowing from the thorium content, which may result in slightly stronger contrast when shooting monochrome film. Comparing its rendering against later non-thorium Summicrons is sure to spark the curiosity of enthusiasts.
An especially early serial number among the sub-one-million radioactive Summicrons, and furthermore, an exceptionally well-preserved example retaining its original condition.

Previously sold by our shop, this rare piece has now made its way back to us after passing through the hands of several owners. Welcome back!
We are truly grateful whenever such a rare item in superb condition finds its way home again 🙏
Just as when we last sold it, this lens remains in exceptionally clean condition with very little sign of use. Even the collapsible barrel section shows minimal wear, and the chrome plating retains a beautiful shine.
For this resale, the lens underwent another full overhaul in May 2026 as a precaution. Thanks to the careful servicing, every control operates with remarkable smoothness. The locking action of the collapsible barrel has been tuned to a perfectly satisfying torque, making operation completely stress-free. Rangefinder coupling is spot on as well.
A few extremely faint cleaning marks can be seen on the front element, but for a thorium Summicron, the glass is astonishingly clean. There is no haze or fungus damage, and the optics remain beautifully clear and transparent. You can fully enjoy the razor-sharp rendering characteristic of the radioactive Summicron.
Comes with original front and rear caps.
A truly hard-to-find condition example!