This is a composite image which illustrates one form of Engine Turning (top half) and one style of Spotting (bottom half).
Since the top half of the image is from an image in the public domain and the bottom half is from an image licensed under either the GNU Free Documentation License or the Creative Commons Attribution-ShareAlike 3.0 Unported license, the resulting composite image as a whole is also licensed under either the GFDL or the same Creative Commons license.
The top image is a portion of an image from Wikimedia Commons. It is by the Wikimedia user "Watchexpert," and has been placed by the photographer in the public domain. Original location: http://commons.wikimedia.org/wiki/File:Guilloch%C3%A9-Muster_auf_Uhrwerkplatine_01.jpg Here is the entire original image:
The bottom image is a portion of an image also from Wikimedia Commons. It is a photograph of a Type 57SC Bugatti engine by Wikimedia Commons user Sfoskett, and is of a vehicle in the Ralph Lauren collection on display at the Boston Museum of Fine Arts in 2005. License: GFDL or CC By-SA 3.0 Unported. Location: https://commons.wikimedia.org/wiki/File:RL_1938_Bugatti_57SC_Atlantic_engine.jpg. Here is the entire original image:
