There are two ways to do this:

1) Under the “Fields” tab, open the “openfunds fields v…” PDF and in the PDF reader search for the term “//No longer supported.//” (with the forward slashes, but without the inverted commas).

2) Alternatively, you can open the Excel file from the same location. On the right hand side are two columns: “Introduced” and “ValidUntil”. These two columns indicate which version was in use when the field was inserted and when it became //No longer supported / / respectively.