| Underwood & Underwood Advertising view (uncertain) n.d. Stereoview, detail Jefferson Stereoptics Courtesy of John Saddy (Auction, Tues. August 29th & Thurs. August 31st, 2006, # 06-3, Lot 753) LL/13877 The image shows four Becker style viewers of various size, numbers 1,2,3 & 4
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