[Spike]

National Chicle fine pens (R313) make the most sense to me as the "Photo Art" promo mentioned on Batter Up wrappers. Kids bought the gum, gave the wrapper to the store owner, and got an R313 fine pen. I wouldn't worry about "1200 different" as a misprint, since card makers of the era overestimated their set sizes routinely.

Just like National Chicle added R344 Rabbit Maranville's "How to..." posters to some Batter Up packs, it's possible they used these rare premiums as another wrapper exchange promo in the last days of Batter Up distribution.

On the other hand, because so few exist in the hobby, couldn't they instead be proofs from National Chicle's bankruptcy materials? Goudey bought Chicle's remainders in 1937 and sold them to collectors in the 1960s after Goudey's own failure in 1961. We know that Goudey repurposed Chicle's Maranville booklets onto existing R303 premiums, but wouldn't need to replace R303 itself with these near-identical sepia & brown photos. If Burdick didn't know they existed, it at least hints these photos weren't distributed (and didn't enter the hobby) during the 1930s. Goudey's batch sale to collectors in the 1960s are another possible avenue.