Well, for my 2 points I'd say that we're never likely to know what Nos 17 and 23 are!

I'm inclined to agree with both MMario and Giac about the identification of Nos 7 and 15. Dives and Lazarus is generally assumed to be first recorded here, so about 8/10 confidence. I'd be interested to know how soon afterwards versions of Tam Lin appear in print ... my Forum Search is timing out, so unless it appears in a thread title (which it probably does) I won't be able to look.

:-)
Ian