Anyone interested in the work of the German Standards Institute (DIN) on the General Principles of Proper Patent Valuation can download a copy of the publicly available specification here. You will need to register with the Beuth Publishing House - but the specification is free of charge. Search for the reference number PAS 1070 if the document is not displayed directly. On the top right hand corner there is a button for English language text if the text of the website appears in German.
As mentioned on the IPKat website, ISO is currently considering a work proposal to define an international standard on the valuation of patents and has sent out a letter to its member organisations asking for their comments on whether ISO should develop a standard.
