Fret saw.
Cerve 0,45mm
Blade 0,4mm
260mm lon
17 tpi cross cut pull stroke
As it seems Gratsägen (Saws to cut the grooves for sliding dovetails) are not longer made by industry. So I was asked. This took much longer than I anticipated. I made a pair to have a back up.
Afte a few years I made a second spline saw.
1,6mm wide kerf vor splines to connect mitred box sides.