BIOS Version

You can check the current BIOS and ECP versions on your ThinkPad by using dmidecode. For example:

# dmidecode -s bios-version

1RETDRWW (3.23 )

# dmidecode -t 11

# dmidecode 2.9
SMBIOS 2.33 present.
Handle 0x0029, DMI type 11, 5 bytes
OEM Strings
        String 1: IBM ThinkPad Embedded Controller -[1RHT71WW-3.04    ]-

Showing BIOS version 3.23 (1RETDRWW) and ECP version 3.04 (1RHT71WW).

Alternatively you can grep the information from dmesg

$ dmesg | grep "ThinkPad BIOS"

[    3.758331] thinkpad_acpi: ThinkPad BIOS 6DET52WW (3.02 ), EC 7XHT22WW-1.04