For my own edification I am reverse engineering a P65A Op-Amp made by Philbrick Research in 1962. I know I could probably find the schematics somewhere but I want to learn, including identifying components. The component pictured looks like a diode, is marked with 102K on one side and 12BY and 7843 on the unseen surface. I would assume it's a 102 K resistor but 102K seems way out of proportion to the other components and I've seen capacitors marked with 270K being 27 nF. So is this an axial polypropylene capacitor with a 1nF value or is it a 102k resistor or is it even a diode?
While there's more than one thing it could be, my first guess would be a 1nF cap, \$\pm 10\%\$. For a more final determination, you can either draw it into the schematic and see if it looks right, or take it out of circuit and test it.
I needed to refer to external memory for the tolerance code; the first page that came up when I searched on "capacitor value markings" was this one.