Recently I had some guests stay for a while, and while they were packing and cleaning this pen rolled out of a bedroom closet. I can't find any identifying marks on the pen itself anywhere, and in fact it looks quite a bit different inside than any pen I have seen before (not that I have tons of experience)--it's just a completely hollow tube made of very thin metal, with a friction-fit cap that holds a #773 R. Esterbrook & Co's Natural Slant, also friction fit and with no reservoir to speak of.
The only information I can find on the nib is that the nib is possibly from around 1938, or at least that that model was being manufactured at the time (The Esterbrook Project).
The house where this was found was constructed in ~1939, and I have no idea how long the pen was hiding in the closet since we've cleaned it out several times before and it wasn't even the first time this month that we had guests staying in that room. We're also far from the first owners, though I found a penny from the 1940s when we did a demolition project in the garage so there are some artifacts from the early days of its life still hiding around!
Any pointers would be appreciated! I'm not sure what to call the raised vine and flower motif on the outside to help narrow my searches to try to find similar pens by blind luck.
Looks like a dip pen like we used in school (art, calligraphy, not normal writing), with a more elaborate handle than we used, though.