This is a Kodalux L Shoe Mounted Meter, which I also believe was sold as the Gossen Sixti. This is a beautiful little accessory shoe meter made in Germany (the build quality shows). The meter is a capable of both reflected and incident readings. The readings agree well with my Sekonic Studio Pro. This meter is perfect for use on a meterless rangfinder, SLR, or medium format camera.
Sold with finely made original leather case.
Here are some Web links with more information:
Price: $40 plus shipping. I ship worldwide and I accept PayPal