Does anyone have any clues as to what the last three letters on Thinkpad's stand for? For example, my T400 is a 7417CTO. What does the CTO stand for?
Lenovo Think systems are identified by a system model type which is 4 digits, and then sub-model designation of three alpha numeric characters. In the example above, the Model 7417 is a member of the T400 ThinkPad family, and the sub-model type is CTO which stands for Configure To Order, which means it was ordered directly from Lenovo as an individual customized configuration.
In addition to custom models, Lenovo offers many pre-configured, standardized configurations. Each of these particular combinations of system family, processor speed, installed memory, hard disk type, graphic processor, networking cards, preloaded OS and many other options are coded as a particular three character sub model.
Together, these seven character combinations uniquely identify the specifications of a system and are available to view in the product reference sheets. http://psref.lenovo.com/
Warranty entitlement and system build information is stored in Lenovo systems and can be accessed by keying in the 4 digit model type and a particular system's unique serial number on the support site. www.lenovo.com
Look for the model type and serial information on the bottom of ThinkPads. Some newer models with removable batteries may include this information in the battery compartment (remove the battery to find it) or in the case of some tablets, it may be included behind one of the removable doors.