Exhibition labels and the back of a print
A print on a wall shows one frame. A small code on the label shows the other two hundred — the series it came from, the technical notes, the work that didn't make the wall. Galleries and open studios have quietly standardised on this, because it adds depth without adding text to the label.
The back of a print is the other classic placement. A code there survives framing and resale, and it's the closest thing a physical photograph has to metadata that a future owner can actually follow.
Keep it discreet and keep it dark. A 1.5–2cm code in the corner of a label is enough at reading distance, and plain black on white is both the most reliable and the least distracting next to work that's meant to be the thing people look at.
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