This is pretty good. Where did you get the 68MB file from? Can you tell us the specific steps you used to produce this?
Starting with the list from the exhibition ... http://www.loc.gov/exhibits/empire/object.html
... I copied the name of the image - in this case: 'Group of Jewish Children with a Teacher'
I went here ... http://lcweb2.loc.gov/pp/mdbquery.html
and searched for the text.
Following the results leads to this: http://memory.loc.gov/pnp/prok/01800/01861u.tif
... the hi-rez B&W triptych.
I opened in ACR and did a little sharpening, opened in aRGB and zoned out the three areas of the positive B&W and made 3 individual aRGB tiffs.
I used AutoPanoPro to align them in a planar projection. I saved them as individual 16 bit tiffs.
I opened the files in PS ... created a new, blank aRGB image ... copied the b/g layer from each file into the appropriate channel on the channels pallet of the blank file and re-touched from there.
It was easier than I thought it would be.
I'm gonna work on other methods of alignment.