Scan Can needs a document-feeder scanner to scan back issues. ETCL has a networked scanner that has recently re-entered use after a repair. Unfortunately, it wasn't working very well over the network. It took quite a while to sort out, but the short version is:
The networked scanner needs to be on the same physical network as the computers accessing it.
The computers accessing it need to have an app installed called "Epson Scan Settings" in the Utilities folder (for OS X) and the Scan software, which also installs the TWAIN driver for PS and so forth. The name of the disk image I found is EXP10000XL_EScan_OSX_30y.dmg
There is another app that one uses to actually set up the scanner. It's called "EpsonNet Config" and gets installed by the installer mentioned above.