HP67 Manual Revisions

[Siegfried]

While shuffling around stuff in my study I found out that I somehow acquired two HP67 manuals. I have a somewhat nicer looking April 1977 Revision D and a little more "experienced" October 1978 Revision E.

As I don't have a HP97 manual yet, I'd be tempted to swap one of them (or sell it to buy a HP97 manual).

Would anyone happen to know what is different between the two? The index looks identical.

Thanks!