This plane has me baffled. Perhaps one of you will recognize it and tell me exactly what it is used for. It has a runner on the bottom 2mm thick by 11mm high. There are no spurs or fences. Only the cutter. The cutter is made in a "T" shape and sharpened with a round file/stone. The cutter is 5mm at it's widest and 3mm at it's narrowest. The cutters "T" is 1mm thick. It appears that a groove about 2mm would first be cut in the board, followed by this plane. I suppose that repositioning the blade would allow a deeper "T" to be cut. Thanks for all responses. Added picture of how it cuts wood (one pass after slot cut).
Bronze plane 1.jpgBronze plane 2.jpgBronze plane 3.jpgCutter 1.JPGCutter 2.JPGCutter 3.JPGwood.JPG