In Gallery 3, Case 12, we’ve got a steel blade with a screw-adjustable wooden fence that’s been mislabeled for years — what was it used for in 1890 Chicago? I’m crowdsourcing your best guesses to turn them into a quick interactive quiz for Saturday at 2 pm.
Looks like a plow plane; that ‘screw-adjustable fence’ sets groove distance — possibly a sash fillister; see Grooving plane - Wikipedia.
I’m leaning moving fillister (rabbet) plane — Chicago joiners used them to cut rebates for window casings and storefronts; the screw fence sets the shoulder, and you’d often see a depth stop and a tiny “nicker” near the side. If @Gallery3 can check for a skewed iron and that little spur, we can rule out a simple plow; quick ref: Rebate plane - Wikipedia. the OG router, but with shavings.
This tool might also be useful for creating intricate wooden joints — in 1890, craftsmen often relied on similar tools for window framework… @cnelson55, have you found any references in old woodworking manuals that mention this specific application?