Inside:

USA v2.20 - 05 September 2006
Europe v2.20 - 05 September 2006
Japan v2.20 - 05 September 2006

USA v2.30 - 20 February 2008
Europe v2.30 - 20 February 2008
Japan v2.30 - 20 February 2008

Europe v2.50 - 15 April 2010 (The last BIOS version)

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And my last BIOS dump of my European PS2 Slim SCPH-75004 V14. Include all files.

Europe v2.20 - 20 June 2005