I had to try it myself to see. I have a modern Epson inkjet photo printer.
I got an old trade card with a blank back and I sanded the back off with 150 grit sandpaper.
It had a pencil notation and it came right off. The back was noticeably more porous after sanding. I figured a stupid forger wouldn't re-size the back with gelatin or some other paper size before printing.
I got a high resolution image of a Cycle back and imported it into Photoshop. I had to make the background transparent or else it would print the background color: white if B&W or light brown.
This is kind of difficult to do without erasing tiny pieces of the border or the serifs. I had to play around with it for a while before getting a good result.
I finally printed it, and it came out like shit. Exactly how I predicted it.
Notice how dead it looks. The serifs are just blurs due to the feathering.
Now, how could the results have been better?
Instead of sanding, could the back be bleached?
If the back is bleached, it would glow under UV light. Probably a bad choice.
Instead of an inkjet printer, was a laser printer used?
A laser printer would produce crisper lines and most laser printers use oil based inks that wouldn't feather as much as the water based inks of inkjet printers. Laser is probably the way to go.
Does the printer leave a signature under magnification?
Yes, the inkjet dots are clearly visible. With a laser printer, probably less, but still visible.
