This probably has been discussed before, the Nash post is from 2013, but as a friend of mine just asked me about Spence, I found this on a search and hope to get some reaction from the experts here. Nash's research as always seems meticulous but I am aware of his reputation. If Spence truly has made so many major mistakes, how meaningful can his authentication be?
http://haulsofshame.com/blog/?p=26228
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My avatar is a sketch by my son who is an art school graduate. Some of his sketches and paintings are at
https://www.jamesspaethartwork.com/
He is available to do custom drawings in graphite, charcoal and other media. He also sells some of his works as note cards/greeting cards on Etsy under JamesSpaethArt.