From Forum Nokia Wiki

The S60 platform is a popular smartphone platform. It has many version starting from S60 version 0.9 (Symbian OS 6.1) to S60 5th Edition (Symbian OS 9.4). Older platform might not support some feature that newer platform introduced it, for example Sensor APIs may not available on some older S60 version, so it is frequently require to warn users attempting to install on incompatible version.

These incompatibility may also be a device specific, for example some device does not have camera.

Platform ID is unique across all S60 platform version, so it is easy to warn user based on Platform ID for incompatible version. This article have list of Platform ID starting from S60 1st Edition (0.9) to S60 5th Edition, which helps developer to put warning message for incompatible version. MachineUid will help developer to create device specific installable.