I was thinking about this for many months
You can provide print option near each coin year, also you can sell the printer which does the job.
This printer should print on coin holder or on some paper which we can stick it in coin holder.
Also you should allow us to decide what can you printed , like country name , KM, Year...etc , it should be available in print setting.
I thought about this too and there're some alternative options:
1) use a label printer that print 100x100 or 100x180 adhesive labels for parcels. it can print many labels on one adhesive paper
2) use a "labeler" that print on thin adhesive tape. the tape is much more expensive than label papers in option 1) and typing is not as easy. but it can be used for printing country names, because the quality of label is better, and it can be removed without leaving adhesive on the sleeves
3) customize one or a few different roller seal with K, M, Y, # and numbers, for KM and Years respectively
4) print label on thin paper (thinner than A4 paper used at office), fold the label, stuff into the pocket using the holder. you don't need to reprint label when replacing the coin
