What do Archivists do all day: Detective work

You may have seen our tweet about what archivists do all day: http://peelarchivesblog.com/2015/07/16/what-do-archivists-do-all-day/

Well here’s what we did on Friday:

We have an undated portrait of Mrs North, the onetime Chatelaine of Avery Hill, by P. Tennyson Cole.Mrs J T Noth by P Tennyson Cole 1887

We know that it must be pre 1891 because it appears hanging in her Boudoir in a photograph of that date.AH_PN_7_14_Mrs North's BoudoirWhile putting a table into an under stairs cupboard on Friday I spotted the corner of an old picture frame. Here its is after cleaning.The frameWe think it is the frame in the picture as there were remnants of red velvet on the border. Then we found the label on the back.The labelThe date 1886/7 seems to have been added later. We know that Tennyson Cole painted Emma North in 1886, but in our other portrait of Mrs North dated 1880, the sitter appears to be more than 10 years younger than in the later painting. What do we do next?