I followed the instructions at http://who-t.blogspot.de/2014/12/building-a-dpi-database-for-mice.html to measure the DPI of another USB mouse. The result is to be found below:

# Chicony 2.4G Multimedia Wireless Kit MG-0919
mouse:usb:v04f2p0963:name:Chicony 2.4G Multimedia Wireless Kit:
 MOUSE_DPI=1000@142

$ udevadm info /dev/input/event19
P: /devices/pci0000:00/0000:00:13.0/usb7/7-3/7-3:1.1/0003:04F2:0963.000B/input/input25/event19
N: input/event19
S: input/by-id/usb-Chicony_2.4G_Multimedia_Wireless_Kit-if01-event-mouse
S: input/by-path/pci-0000:00:13.0-usb-0:3:1.1-event-mouse
E: DEVLINKS=/dev/input/by-id/usb-Chicony_2.4G_Multimedia_Wireless_Kit-if01-event-mouse /dev/input/by-path/pci-0000:00:13.0-usb-0:3:1.1-event-mouse
E: DEVNAME=/dev/input/event19
E: DEVPATH=/devices/pci0000:00/0000:00:13.0/usb7/7-3/7-3:1.1/0003:04F2:0963.000B/input/input25/event19
E: ID_BUS=usb
E: ID_INPUT=1
E: ID_INPUT_KEY=1
E: ID_INPUT_MOUSE=1
E: ID_MODEL=2.4G_Multimedia_Wireless_Kit
E: ID_MODEL_ENC=2.4G\x20Multimedia\x20Wireless\x20Kit
E: ID_MODEL_ID=0963
E: ID_PATH=pci-0000:00:13.0-usb-0:3:1.1
E: ID_PATH_TAG=pci-0000_00_13_0-usb-0_3_1_1
E: ID_REVISION=0101
E: ID_SERIAL=Chicony_2.4G_Multimedia_Wireless_Kit
E: ID_TYPE=hid
E: ID_USB_DRIVER=usbhid
E: ID_USB_INTERFACES=:030101:030102:
E: ID_USB_INTERFACE_NUM=01
E: ID_VENDOR=Chicony
E: ID_VENDOR_ENC=Chicony
E: ID_VENDOR_ID=04f2
E: MAJOR=13
E: MINOR=83
E: MOUSE_DPI=1000@142
E: SUBSYSTEM=input
E: USEC_INITIALIZED=530729189