One code per placement, so you can tell them apart
The same poster in four places with four codes answers a question no single code can: which placement was worth paying for.
Make them a campaign
Group the four codes into a campaign and the reports treat them as one thing when you want a total and four things when you want the comparison. Tags cut across campaigns, so "outdoor" or "Q3" can span several of them.
Comparison is subject against subject: two placements on the same axes over the same dates, rather than two screenshots side by side.
Down to what it earned
With the tracking snippet on your site, a scan that turns into an order reports the order value back and is attributed to the code that started it. That turns "the station poster got more scans" into "the station poster earned more", which is a different conclusion often enough to matter.
Print deadlines and destinations
The destination does not have to exist when the artwork goes to press. Point the codes at a holding page, print, and repoint them the day the campaign starts.