I can't imagine this sheet was produced at any great remove from the time the production cards were printed. Maybe it's some sort of sheet for something else like a related advertising effort, but I would think that there would be some indication of that on the item and it wouldn't just line the cards up like an uncut sheet with normal backs, but would have a different layout like we normally see on posters. It doesn't fully fit into a likelihood of a pre-production test or a production sheet either though; none of the three options really line up to what I would expect or find likely.
One of the best things about uncut sheets of this vintage is that they are so rare (and usually destroyed after discovery) and we have so little evidence about them from the surviving cut cards that when one does appear and we see one there is some surprise that people wouldn't expect.
Incidentally, I am suspicious the checklists with 18 cards are in error, probably taking a PSA label or something as a confirmation. These cards are not super easy but they also aren't that rare and I still can't find any copy of the Jem Smith from the Heroes of the Ring. PSA has only 1 in the POP report, 7+ of all the other cards (Dick Burge being the lowest, not because he's any rarer but because nobody knows who Dick Burge is). This is probably PSA just not knowing the difference between all the Ogden's sets and then people using PSA as a confirmation (hence my love for gathering scans to prove a card
). Thus my earlier questions about the missing boxer from this sheet are null and void, because one is not missing and I can downsize my checklist. It's nice to trim a card off my wantlist without spending a penny
.