Many thanks for all the help I received here! I've now built 4 of the many windows I need for my old cottage.
Sash's are reclaimed old cypress, with new growth cypress jambs. Insulation is spring bronze. They're single hung guillotine style.
The goal of this was to match the old windows that are in the original cottage.
This has been so much fun and so satisfying, I think I'm keeping my wood working equipment and building a shop next.