Seems the RX680, RX685, RX690 has a suitable trapdoor in the rear as well if this image is to be believed.
http://files.support.epson.com/faq/images/pm_paperload_210_er.gif
Confirmation or photos to support this would be appreciated.
Confirmed:
http://www.goodgearguide.com.au/mim.php/prodid/5106/vid/0/angleid/4/resid/2
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Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680