This is a ThumbsUp TU-EP-1 thumb rest grip made by matchTechnicalService, a standard accessory specifically for the Leica M9 / M8. It seems to be less common these days, perhaps due to the Kodak CCD boom of the M8 and M9. It's almost 20 years old, but as the photos show, the brass is starting to show through, giving it a cool, aged look. How about improving the handling and dressing up your LEICA M8/M9 when taking photos? This product is made exclusively for the M8 series and M9 series. Please note that it is not compatible with the M10, M11, and TYP240 series. Thank you for your consideration.